Across:
1 Shutdown (OUT OF BUSINESS) is not working (OUT OF BUSINESS),
10 A foreign (French ‘a’ = UN-) state (= homophone indicator) school on the Thames (‘Eton’ = -‘EATEN) (UNEATEN) is left untouched, of course (UNEATEN),
11 Turns up (= reverse indicator), American (-A-) writer (Ed = -DE-) is not (not) short (t) (‘not’ without ‘t’ = no = -ON-) in old city (UR = R-U) (RONDEAU) – there’s a certain poetry to that (RONDEAU poem),
12 Range (OVEN) of leads, osmium, vanadium except nickels (leads ‘Osmium, Vanadium Except Nickels’ = OVEN),
13 Scot (Scot) free (= anagram indicator) (Scot = STO-C) around island (-I) (STOIC) for one from School of Philosophy (STOIC),
15 Repeat (ECHO) insult coming from touchlines (‘insult’ coming from ‘touchlines’ = oche = ECHO),
17 On holiday (OUT) with most of those in 3 down (most of ‘outs’ = OUT),
19 Old-age pensioner fails to get alongside (‘old-age pensioner’ fails to get ‘alongside’ = epnoer = OPENER) for first game (OPENER),
21 Gangster (Al Capone = -AL-) in damp (wet = WE-T-) hotel (-H) (WEALTH) with means (WEALTH),
22 Fool (LUNATIC) show-off (= anagram indicator) in a cult (in a cult = LUNATIC)
23 Bar (EXCEPT) portion (excerpt) doesn’t include side of rolls (side of ‘Rolls’ = r) (‘excerpt’ without ‘r’ = except = EXCEPT),
25 Stumble along (TOTTER) Dodder (TOTTER),
27 One of those on the computer (KEY) produced code (KEY),
29 Summit (HEAD) on the outskirts of Hemel Hempstead (on the outskirts of ‘HEmel hempsteAD’ = HEAD),
30 One can’t win (LOSER) with philosopher dismissing hip-hop (‘philosopher’ dismissing ‘hip-hop’ = lsoer = LOSER),
31 Summer treats (ICES) back (= reverse indicator) for those in Chinese Cinema (those in ‘chineSE CInema’ = seci = ICES),
34 Start off (r) confirmation (rite) (‘rite’ without ‘r’ = ITE-) for judge (-RATE) (ITERATE) to go over again (ITERATE),
35 Relative (MA = M-A) admits one (-I-) local drunk (-LIT-) on island (-I-) (MILITIA) is fighting civilians (MILITIA),
36 Has no sympathy presumably (OUT OF KINDNESS) for why altruist showed goodwill (OUT OF KINDNESS).
Down:
2 The neighbours (UK-), the Spanish (‘the’ Spanish = -EL-) and the French (‘the’ French = la) retiring (= reverse indicator) (la = -EL-) – what’s the point (East = -E) (UKELELE) in getting played by a plucky sort (UKELELE),
3 Exposes (OUTS) those characters starting for all sides today (‘out’ on all sides of today’s grids = OUTS),
4 Buckle (= anagram indicator) in boot (in boot = BONITO) a little fishy? (BONITO),
5 It’s art (its art) broadcasted (= anagram indicator) (its art = STRAIT) by channel (channel/passage = STRAIT),
6 Religious (NUNS) school (National School = -NS) after (= position indicator) a French (‘a’ French = un) Revolution (= reverse indicator) (un = NU-) (NUNS),
7 Client’s (clients) boss (= anagram indicator) (clients = STENCIL) employed by the sign writer (STENCIL),
8 Is no longer bothered (OUT OF ONE’S HAIR) presumably where dandruff comes from? (OUT OF ONE’S HAIR),
9 Safe (OUT OF HARM’S WAY) is not at risk (OUT OF HARM’S WAY),
14 Not in (OUT-) Times for number of years (-AGES) (OUTAGES) – those with power are to blame for these failures (OUTAGES),
16 Pitches in (HELPS) The Alps without a T…? (‘the alps’ without ‘a t’ = helps = HELPS),
18 No gas found in God’s acre (no ‘gas’ found in ‘Gods acre’ = odcre = DECOR) by design of The Creator? (DECOR),
20 You don’t want to get stuck (stuck in a RUT) in this revolutionary (= reverse indicator) part of structuralism (part of ‘strucTURalism’ = tur = RUT),
21 Waiter hasn’t got ear (‘waiter’ hasn’t got ‘ear’ = wit = WIT) of comedian (WIT),
24 Could start (‘Could’ start = C-) to not be able to stomach (-HATE-) a (-A -) classy (-U) (CHATEAU ) nice source of wine (Nice/French wine from CHATEAU),
26 Diplomacy (tact = TAC-T-) over one (-I-) going to America (-US) (TACITUS) with old historian (TACITUS),
27 It’s okay (ok) going back (= reverse indicator) (ok = KO-) to find missing first (s) bit of dust (speck) (‘speck’ without ‘s’ = -PECK) (KOPECK) in eastern capital (capital/money = KOPECK),
28 First to yell (first to ‘Yell’ = Y-) out (= anagram indicator) names (names = -ES- MAN) (YES-MAN) to stooge (YES-MAN),
32 Starters of tortilla and chorizo often (starters of ‘Tortilla And Chorizo Often’ = TACO) served in Mexico restaurant (TACO),
33 Dynasty (CLAN) from The Eternal City (from the ‘eterNAL City’ = nalc) going all the way back (= reversal indicator) (nalc = CLAN).