Across: 

5 Facade (ACT) + 1st letters (1st & foremost) of the last 3 words = ACTUAL (concrete)  Architecturally predictable!, 7 Author (I) + blamed (SLATED) with 1st letter (primarily) of (O)xycontin injected (mainlining) = ISOLATED (divorced)  Given what Oxycontin does to people, divorce is but a minor inconvenience!, 9 Anagram (for revision) of CHAP + TIME = EMPHATIC (impressive)  Well, I was impressed when anyone at school did any., 10 Managed (RAN) reversed (to return) + lettuce (COS) = NARCOS (agents)  Clearly they were playing hardball!, 11 Revealed sensitive information about (OUTED) containing (entertaining) project in the sense ‘stick out’ (STRETCH) = (being) OUTSTRETCHED (extended)  There’s always one blabbermouth, 13 DD with D2 being a whimsical reading of LEGEND as LEG END ( ie foot)  Most likely place to find one., 15 WINE from the clue with (W)ife swapped for THE = (for) THEINE (a bit of tea – of which theine is an ingredient)  Not my wife, obvs!, 18 Popular (IN) + sportsman (PRO) + helping (PORTION) = (to become) IN PROPORTION (relatively well-built)  It’s a dream I’ve given up on., 21 Homophone (said) of couple two/TOU + are allowed (CAN) = (to get) TOUCAN (a bird)  We once had a lovely hand-reared Patagonian conure. It shat…a lot!, 22 Anagram (nuts) of RAIDER + HA(s) minus last letter (finally gone) = DIARRHEA (runs with American spelling)  Well, you would, wouldn’t you?, 23 DD with the name of the WW2 air raid shelter and the legendary Jimmy ANDERSON.  I once faced John Snow and Angus Fraser y’know., 24 DBE (maybe) of Reggie (Perrin)’s business (GROT) + (‘s/has) outer letters (extremely) of T(ack)Y = GROTTY (of poor quality)  It actually said so on the sign after all!. 

Down: 1 Justified (DUE) containing (storing) game (CHESS) = (in) DUCHESSE (dressing table)  TBF it needs justifying, 2 Anagram (unexpected) of RESULT = (for) ULSTER (rugby team)  0-0 would do it, 3 Reading of MOONSHOT (something optimistic) as MOON (to place seat in window) and SHOT (attempt).  You ought to give it a try. It ain’t easy!, 4 (S)Salvation (A)rmy + Little CRED(ibility) = SACRED (much revered)  I really can’t comment., 6 (COM)mon + trap (SET UP) reversed (when changing  course) = COMPUTES (figures)  Always a moment of jeopardy., 7 Anagram (dancing) of IT’s NICE minus (dispelling) 1st letter (at the outset) of S(hyness) = INCITE (encourage)  I’d rather pull my own teeth TBH, 8 Anagram (redrafting…as) of PrOSE minus (not) r(ight) = EPOS (a poem)  It’s just not proper And oft comes a cropper (qv), 12 Anagram (moving) of 1st letter (beginning to) of L(ower) + TENSION = INSOLENT (forward)  As our over-enthusiastic transatlantic friends might say, way to go!, 14 Reversal of Hull (POD) + sophistication f(INESS)e minus outer letters (peel away the veneer) = (to reveal) DOPINESS (a narcotic stupor)  with apologies to the much maligned city of Hull, whose motto should really be “It’s not as bad as you think”, 16 Former (EX) + anagram (beaten up) of RIOTER = EXTERIOR (outside)  On the other hand, you know what I just said about Hull…, 17 DD with the imperative HOLD ON = wait, while also meaning to HOLD ON in the sense of endure.  Best strategy when boarding a plane, 18 Starts (fl)INCHES minus opening 2 letters (1st pair wanting) = (to make) INCHES (moves)  Swingers, obviously!, 19 Answer hidden (contains) in kORAN GEnuinely =ORANGE (something rather juicy)  To be quite clear, in an exciting moral/philosophical sense as opposed to some kind of smut!, 20 DD  Probably tastes better than it sounds.