There are usually one or two points of interest in an Azed puzzle, and here we pick them out for comment. Please feel free to add your own questions or observations on any aspect of the puzzle (including clues not listed below) either by using the comment form at the bottom of the page or, if would prefer that your question/comment is not publicly visible, by email.
Azed 2,654 Plain
Difficulty rating:
(3 / 5)
An enjoyable puzzle that was, I felt, definitely trickier than average, featuring as it did a generous helping of obscurities and archaisms.
Setters’ Corner: This week I’m going to look at clue 12a, “Local droning noise spread during transmission of data (5)”. The wordplay here has a three-letter word (past active tense) meaning ‘spread’ or ‘diffused’ (usually applied to colour) inside a two-letter abbreviation which Chambers gives as representing ‘data transmission’. The question this raises is how much latitude setters have when indicating abbreviations which are purely that, ie they would never be seen as having lives of their own as, say, PC or CD might (“My PC doesn’t have a CD drive”), or those ‘volunteers’ in 17d do (“He’s in the ??”). Could ‘tick’ be used for CR (credit) or ‘big’ for LG (large)? We’ve all seen ‘good man’ for ST (saint), but personally I’m not keen. ‘Navy’ for RN is better – at least one of the abbreviated words is there. I’m very happy, though, to accept Morecambisms (all the right words but not necessarily in the right order), so I’ve no problem with ‘transmission of data’ for DT or “constable that’s special” for SC.
Across
6a School science subject in short, child trailing in clumsy patch (5)
I don’t recall this being a subject in its own right at my school, but it’s a three-letter contraction of a six-letter science which must be followed by the usual abbreviation for ‘child’.
14a Disused dagger, ineffective with edge half gone, getting oiled? (7)
A three-letter word meaning ‘ineffective’ or ‘useless’ is followed by one half of the word EDGE and a two-letter slang term meaning ‘on the way to being drunk’ (ie ‘getting oiled’). The answer in the sense of a small dagger is shown by Chambers as ‘archaic’, hence the ‘disused’.
15a Record? Two couples left kept awake when it’s spinning (5)
A nine-letter word meaning ‘kept awake’ or ‘unable to drop off’ must be reversed (‘spinning’) and deprived of the pairs of letters at the start and end (‘two couples left’).
20a Sickly drink? At first swallowing very little (10)
A well-disguised break between definition and wordplay, the latter involving a three-letter word meaning ‘[to] drink’ being followed by a four-letter word for ‘at first’ containing (‘swallowing’) a three-letter adjective (given by Chambers as Scottish, which of course it is, but an rarity it is not) meaning ‘very little’.
26a Sounds ‘ostile in the front, having 18? (8)
A five-letter word which could conceivably mean ‘sounds hostile’ (certainly in the sense of making one’s disapproval of a performance known) is deaspirated in the same way as ‘hostile’ has been and then placed inside a four-letter word for the front (often in a nautical sense). The highly apposite reference is to the solution at 18 across.
27a Alternative to the Vulgate a Catholic mostly recalled (5)
A (from the clue) and a term for a Roman Catholic (or a classical language) from which the last letter has been omitted (‘mostly’) are reversed to produce the solution.
28a Curls tight round either half of hair dressed in a bunch (7)
An anagram (‘tight’) of CURLS is placed round either half of a four-letter word for ‘an elaborately dressed head of hair’ (ie ‘hair dressed’).
30a One should know how to negotiate traffic island, having ingested books (5)
A three-letter island or reef has ‘ingested’ the usual abbreviation for ‘books’ (not ‘NT’ or ‘OT’, which are sometimes indicated in this way, but not by me – see Setters’ Corner above).
Down
3d Centre of faith wavering, broken by severe Islamic services (6)
The three letters at the heart of FAITH (‘centre of faith’) are rearranged (‘wavering’) around a word meaning ‘severe’, as a nasty cold might be.
4d The old agree about splitting leave (7)
That oft-seen two-letter bit of commercial jargon for ‘about’ is put inside (‘splitting’) a word of French origin meaning ‘permission to depart’. I did wonder why Azed had chosen a definition which bore such a close resemblance to the archaic (‘old’) answer, but the two obvious options share either their first three letters or their last four with it.
5d Type of vaccine, cube maybe swallowed three times daily (6)
The ‘cube maybe’ which has been ‘swallowed’ by the instruction seen on medical prescriptions for ‘three times a day’ is the sort first produced by Liebig’s Extract of Meat Company in 1910 and sold for a penny each. During World War I, 100 million of the little fellows were apparently sent out to members of the British armed forces as part of a standard set of emergency rations, each in its own individual box.
6d Pass, last dropped, making veteran smoulder? (6)
The name of the pass which forms the border between Italy and Austria has its last letter dropped, producing an obsolete word meaning ‘to burn’.
8d The sound of cavalry approaching line in force? (5)
The usual abbreviation for ‘line’ is contained by a slang term for those comprising a force of law and order, the result describing sounds which would almost certainly accompany the arrival of the cavalry unless the horses were travelling through mud or shod in slippers.
9d Sea mist shrouding rees fluttering in umbellifer (8, apostrophe)
The wordplay here has the four-letter word for a raw sea mist on the east coast of England or Scotland containing (‘shrouding’) an anagram (‘fluttering’) of REES (the plural of ‘ree’, the female of the ruff, if you were wondering). The solution is hyphenated, 5-3.
10d King occupying hidden house rented privately (12, 3 words)
The monarchical abbreviation for ‘king’ is contained by (‘occupying’) an anagram (‘hidden’, an interesting choice of indicator) of HOUSE RENTED. The (5,3,4) solution is a literal translation from a (3,4) Latin expression. According to Brewer’s, “The origin of the phrase is obscure but the story is that Cupid gave Harpocrates (the god of silence) a ????, to bribe him not to betray the amours of Venus. Hence the flower became the emblem of silence and was sculptured on the ceilings of banquet-rooms, to remind the guests that what was spoken sub vino was not to be repeated sub divo.”
17d Riding east, stop taking in volunteers (8)
You might think that following the usual abbreviation for ‘east’ it was a four-letter verb meaning ‘[to] stop’ which is containing the two-letter abbreviation for a group of volunteer reservists, but that would leave us a letter short of the solution. The ‘stop’ is in fact an organ stop, a fifth above the basic pitch (I don’t profess to know what that last bit means).
19d Grass ignoring cue to spill the beans, owning up (7)
A six-letter grass has the consecutive letters CUE removed (‘ignoring cue’) and is followed by a word meaning ‘to spill the beans’ (in a way that might be likened to a canary).
28d Even though old-fashioned he wrote memorable plays (5)
The second definition here is the surname of the American playwright probably best known for Who’s Afraid of Virginia Woolf?, first staged in 1962, and deserving of fame for its name alone. I am put in mind of a music critic who observed that the band Blue Öyster Cult “write better titles than most bands write songs”.
29d Climbing lowest end of range, e.g. Atlas? (4)
A three-letter word for ‘lowest’ and the last letter (‘end’) of ‘range’ are reversed (‘climbing’) to produce an archaic term for the type of being that Atlas personified.
(definitions are underlined)

(2 / 5)
(2.5 / 5)
(3.5 / 5)
(4 / 10)
As you state, requiring synonymy of strict definitions precludes too many commonly-accepted replacements. Figurative language is often in broad use, and it does not seem to be a stretch to equate figurative definitions. [With that said: I would not use “gutless” to define “spineless”, as the words have the same endings. “Lacking guts” for “spineless”, however, not only works with their definitions but also suggests wordplay that is absent: a nice bit of trickery.]
All of my grids are themed, and I expend much effort in ensuring that theme words do not intersect, even when the theme is irrelevant to solving or is trivial. Even better, and even when I am likely to be the only person who notices, are grids where the themed entries are symmetrically arranged. My bride, who has no truck with cryptics (“you do you, dude”), is nevertheless the recipient of my commentary, and pretends to be happy for me when I achieve the desired effects. The look of the thing is important for our art, and art it is.
Yes, an obviously asymmetrical grid niggles setter and solver. Conditioned responses, perhaps, but conditioned all the same.