I took a while to work my way through this one, getting into terrible trouble in the south-west corner. But, looking at the completed grid now, I’m wondering what all the fuss was about. A nice puzzle, though there may be one or two quibbles for the purist.
ACROSS
1. PERSPICACITY Per [person] + s [special] + pic [picture] + city [metropolis]
10. INITIAL An odd little double definition; perhaps a nod to the 15² doyenne…
11. TWEENIE Initial letters of To Want Extra Effort Now In Everything
12. BLESS L(eicester) within Bess [good queen]
13. ANCESTRY An [indefinite article] + (dio)ces(ian) + try [experiment]
15. NOT GO AMISS Anagram of got on + a miss [a girl]
16. VEAL Hidden within haVE A La carte
18. TUBA Initial letters of Takes Up Blowing Amateurishly
20. STRENGTHEN Str(ess) + eng [engineer] + then [as a result]
22. ETOUFFEE E [English] + u [university] within toffee [sticky sweet] – a new word for me
24. ROUGH Hidden within thoROUGHly
26. ROSSINI RO [run out] + SS [ship] + in I [in one]
27. HOG-WILD Anagram of old whig
28. MENAGE A TROIS Anagram of organise team
DOWN
2. EMINENT Emin [Tracy, artist] + anagram of net
3. SLIPSHOD Slips [falls] + hod [carrier]
4. ILLS (P)ills [tablets]
5. ASTONISHED Anagram of a hedonist’s
6. IRENE IR [Inland Revenue, former tax authority] + ENE [East North East, directions]
7. YANGTZE Y [algrebraic unknown] + z [last (letter)] within anagram of agent
8. BIG BANG THEORY Big bang [loud noise] + anagram of other + y(ear) to give a somehow unsatisfying &lit
9. JEKYLL AND HYDE Visual pun on the phrase ‘split personality’
14. SMATTERING Matter [affair] within sing [confess]
17. AGAR-AGAR Repetition of a gar [a fish]
19. BLOSSOM Blo(w) [wind] + reversal of moss [plant]
21. HOUDINI Hou [sounds like who] + dini(ng) [feeding] to give the famous escapologist
23. FEIGN Reign [rule] with the initial letter changed
25. WHOA Not sure about this one – a not-very-cryptic definition? Lester Piggott, the jockey, might have stopped his horse by shouting Whoa!
25 looks like a (not quite as satisfactory) version of the Bunthorne classic “Amundsen’s forwarding address? (4)”. At least for me – it was my familiarity with the Bunthorne clue that made this my first one in today.