Across:
8 It’s nonsense (HOT AIR) taking all the characters back (= reversal indicator) to take a left (l) out of Rialto (take ‘l’ out of ‘Rialto’ = riato = -OT AIR) towards hotel (H-) (HOT AIR),
9 Warm (FRIENDLY) rashers and sausages (FR-Y) lined (lined = -IENDL-) up (= anagram indicator) inside (FRIENDLY),
10 Large bird (IBIS) turns up (= reversal indicator) in Novosibirsk (turns up in ‘Novosibirsk’ = sibi = IBIS),
11 Good management (PROVIDENCE) of papers (-ID-) in a part of France (Provence = PROV-ENCE) (PROVIDENCE),
12 Think about (PONDER) corrupt (= anagram indicator) doper (doper = PO-DER) hanging around back of peloton (back of ‘peloton’ = -N-) (PONDER),
14 Member of the Resistance (“resister” = “RESISTOR”) vocal (= homophone indicator) on the circuit (RESISTOR / electric current),
15 9 across (‘friendly’ = FRIENDLY) is a type of feuding (RIVALRY) (FRIENDLY RIVALRY) or good-natured competition? (FRIENDLY RIVALRY),
18 Loud music (forte = -F-) at a foreign (a = -EIN-) restaurant (CAF-E) outside (CAFFEINE) will keep you awake at night (CAFFEINE),
20 Therapists ignore part (‘therapists’ ignore ‘part’ = heists = THESIS) of scholarly argument (THESIS),
22 Colourful type (GREY) from hospital (‘Mater’ = ‘MATTER’) verbalised (= homophone indicator) (GREY MATTER’) with intelligence (GREY MATTER),
24 Anniversary (DATE) of some revolutionary (= reversal indicator) secret administration (some revolutionary ‘secret administration’ = et ad = DATE),
25 Siege can (siege can = AGENCIES) damage (= anagram indicator) the levers of American government (AGENCIES),
26 Figure on the invoice (AMOUNT) for Pinot from mountaintop (‘Pinot’ from ‘mountaintop’ = mounta = AMOUNT).
Down:
1 Two versions of Wellington (boot + boot) not finished (t+t) (‘boot’ + ‘boot’ without ‘t’ = BOO-BOO) – it’s a mistake (BOO-BOO),
2 Forbids (BARS) public houses serving pints (BARS),
3 Cooked a meal (PREPARED) for a scout, for example (scout motto = be PREPARED),
4 Segment of Meatloaf rocks (segment of “Meatloaf rocks” = af ro = AFRO) and is a cut above the rest perhaps (AFRO),
5 Channel Islands (CI-) connections (-TIES) (CITIES) to London and Paris (CITIES),
6 Don’t make a big fuss of (UNDERSTATE) organisation (UN-) with the foreign (the = -DER-) union member (-STATE is a member of the Union/USA) (UNDERSTATE),
7 Everyone (ALL-) is plain to see (-CLEAR) (ALL-CLEAR) and you can’t get any better than that (ALL-CLEAR),
13 Deirdre (DEE-) is inquisitive (prying = -P-RYING) about chef at the foundation (‘chef’at the foundation = -F-) (DEEP-FRYING) making chips (DEEP-FRYING),
14 Boots taken from mother’s boy (‘boots’ taken from ‘mothers boy’ = mhery = RHYME) in Limerick (RHYME in limerick poem),
16 A rare dog (a rare dog = ROAD RAGE) barking (= anagram indicator) drives people mad? (ROAD RAGE),
17 Travel in (travel in = INTERVAL) spring (= anagram indicator) break with refreshments perhaps (INTERVAL),
19 Paramilitaries’ (IRA-) top quartermaster (top ‘quartermaster’ = -Q-) is (-IS) (IRAQIS) living in the Middle East (IRAQIS),
21 Make a plan (INTEND) for Indian agent losing again (‘Indian agent’ losing ‘again’ = indent = INTEND),
23 Water-ski dropping the wire? (‘water-ski’ dropping the ‘wire’ = atsk = TASK) That’s the thing in hand! (TASK in hand),
24 Doing nothing for banks (‘doing nothing for’ banks/sides = DOOR) on the way out (DOOR).