26 across: Harmonious threesomes finally flee such impatient coeds (9)
Brilliant trickery that must have taken a long time to think up: threesomes finally flee such impatient coeds = such – uch + impatient – ent + coeds – eds = simpatico = harmonious.
15 down: Meet single clue — not this type (3, 6)
Despite some protestations, I still reckon this one’s a goodie: single clue — not this type = run across (clue is down, not across) = run across = meet.
22 across: Retired killer gets yonks, strangling flash braggart (9)
Mo seems to be DA favourite of late: retired killer gets yonks strangling flash = retired cain age strangling mo = retired cainamoge = egomaniac = braggart.
21 down: Vaults hoisted by one charter plane (3-4)
Very clever indeed: vaults hoisted by one = atria hoisted x 1 = air-taxi = charter plane.
14 down: … against ex-follower (9)
Such terse elegance: against ex = con former = conformer = follower.
3 down: Stalks onstage, it’s said? (7)
I was too busy thinking of homophones to get this one: onstage it’s said = rhubarb (what actors say on stage to mimic the sound of indistinct background conversation) = stalks.
12 across: Exercise Bureau regularly provides flirtatious apparel (4-2, 3)
A welcome return to the racier side of DA’s oeuvre: exercise bureau regularly = push-up bureau = push-up bra = flirtatious apparel.