11. Weak or strong bar FRAIL (f rail)…
13. Cut over, love following game POLO (lop, rev. + 0) The first pair of trick clues. It was the mismatch of the second O of POLO that alerted Dr Watson to the deception. The solutions are entered as APRIL and FOOL.
14. Matches no longer in use when about exhausted AMATES (mate in as) ‘Exhausted’ leads to mate2, an adjective linked semantically to ‘checkmate’, whereas the Spenserian ‘amate’ is derived from mate1 in the sense of ‘match’ or ‘couple’.
17. English composer rendering poet’s ‘Abode of the Departed’ ADES (2 mngs.) Experienced solvers should have come across Milton’s spelling of Hades, as it crops up in wordplay every so often, but the relatively young British composer Thomas Adès may be less familiar.
19. Kindle going wrong before last bit of title, approaching denouement? ENDLIKE (anag. + e) As far as Dr Watson knows, this is Azed’s first citation of Wiktionary (in the puzzle’s footnote) in support of a solution, and it allows your reviewer to share this link. ‘Endlike’ isn’t in OED, but the online source finds it in a line from Finnegan’s Wake.
30. Rhyming scheme for chart-toppers? ABBA (i.e. A-B-B-A) This idea has certainly been used before, but it’s too good to pass up.
35. Alternative to bell-ringing? Single one could replace setting altar RAT-TAT (comp. anag.) A very well concealed comp. anag. in a not entirely coherent surface reading. ‘Single rat-tat’ is an anagram of ‘setting altar’.
36. Stoop (as once), looking anaemic by the sound of it PAIL (‘pale’; see stoup1)…
37. Start of last over? Coming in aimed at stump FLOOR (l o in for) The second suspect pair, this time entered as FOOL and APRIL respectively.
38. Pour out regular feature of bad language EFFUSE (i.e. eff use, or FU’s) Effs might well be used by some solvers on discovering the trick solutions, but this clue will surely be the favourite of the puzzle.
3. Such as Bunthorne taken off in satire ARTIES (anag.) The reference is to the effete and ‘fleshly’ poet of Gilbert and Sullivan’s Patience. Many solvers will also fondly remember Bob Smithies, the late Guardian setter who borrowed his name.
6. Hang where some take the plunge, cutting end of rope? DEPEND (de(e)p end) A rather brilliant subtraction clue.
12. Decision from the Élysée, showing where it stands, almost, and about time! PARTI (t in Pari(s)) The Élysée Palace is currently the official residence of Emmanuel Macron.
20. Irish resort, fashionable, amid varied lakes KINSALE (in in anag.) The first of two geographical solutions is the Irish western coastal town of Kinsale.
19. Do part of dressage routine? One did it, entering prize PIAFFE (a ff in pie) Chambers gives ‘luxury or prize’ as one meaning of pie1, and ff. can abbreviate the Latin fecerunt (they made it) as well as the commoner fortissimo. A piaffer, which gives rise to the verb that is the solution, is apparently a trot, but slower.
25. City in Italy beneath rocky tier RIETI (anag. + I) The Apennine city of Rieti was new to Dr Watson, but it does look as though its situation justifies a semi-& lit. appellation for the clue.
Across: 1. SNEAPED (ape in sned); 6. DARGAH (anag.); 15. SPAMMER (maps, rev. + mer (Fr)); 16. PERICOPE (eric in Pope); 18. ESTEEM (m to end in mestee); 26. INSTEPS (in steps); 29. STEINS (in in sets, rev.); 32. PASTNESS (sent, rev., in pass); 34. FOOT ROT (tort oof, rev.); 39. ROSE-RED (R + os(I)ered).
Down: 1. SLAP (pals, rev.); 2. NAMESON (anag. in nan); 4. PIECES (2 mngs.); 5. DISPENSATOR (pens in anag.); 7. AFALD (L in a fad); 8. ROMAL (comp. anag.); 9. ALEE (hidden rev.); 10. HIRSEL (anag.); 22. OPPOSE (anag. + SE); 23. ATTAPS (tap in ATS); 24 VENTRE (v + entre(at)); 27. TATOU (hidden); 28. EARLS ((p)earls); 31. BOFF (boff(in)); 33. STUD (2 mngs.).