Across:
8 The odd supper (odd letters in 'SuPpEr' = SPE-) from Spain (-E-) that's cold (-C-) and hot (-H) (SPEECH) in a manner of speaking (SPEECH),
9 Corrupt (= anagram indicator) director (director = CREDITOR) is owed money (CREDITOR),
10 Expertise (GIFT) in a ward? (‘a ward’ = ‘award’ = GIFT),
11 Relates to the pips (TIME SIGNAL) in giant limes (giant limes) all over the place (= anagram indicator) (giant limes = TIME SIGNAL),
12 Fragment (SNATCH) of anarchic (= anagram indicator) chants (chants = SNATCH),
14 Hurry up (STEP ON IT) and put your foot down (STEP ON IT),
15 They’re a comfort to those retiring (HOT-WATER BOTTLES) in deep trouble (HOT-WATER) taking courage (BOTTLE-) on top of stoicism (top of ‘Stoicism’ = -S) (HOT-WATER BOTTLES),
18 Range (SPECTRUM) of mushrooms (ceps) served up (= reversal indicator) (ceps = SPEC-) for tea (-T-) from the bar menu (-RUM) (SPECTRUM),
20 Single out (PICK-) the French (‘the’ French = -LE) (PICKLE) in hot water (in a PICKLE),
22 Seal sets in (seal sets in) box (= anagram indicator) (seal sets in = ESSENTIALS) with must-haves (ESSENTIALS),
24 See-saw (YO-YO) or swing? (YO-YO),
25 Going on a long arduous journey (TREKKING) in train primarily (‘Train’ primarily = T-) with Reginald (Reg = -RE-G) taking in weekend (‘weeK’ end/last letter = -K-) with family (-KIN-) (TREKKING),
26 Frog’s place perhaps (frog in THROAT) in Dartmouth when mud is removed? (‘Dartmouth’ when mud is removed / without ‘mud’ = artoth = THROAT).
Down:
1 Another (= anagram indicator) potion? (potion = OPTION) Take it or leave it! (OPTION),
2 Copper (CENT) from Cologne (scent) loses the head (s) (‘scent’ without ‘s’ = cent = CENT),
3 Tom (C-AT) admits difficulty (-HIT-CH-) (CHIT-CHAT) with small talk (CHIT-CHAT),
4 Run (r) away from 14 down (‘scram’) (‘scRam’ without ‘r’ = SCAM) – it’s a shady deal (SCAM),
5 Even older sister (even letters of ‘oLdEr SiStEr’ = LESSE-) close to home (close/end to ‘homE’ = -E) (LESSEE) is one paying a flat fee (LESSEE),
6 A distinctive problem (DIAGNOSTIC) in upsetting (= reverse indicator) papers (ID papers = DI-) by religious sceptic (-AGNOSTIC) (DIAGNOSTIC),
7 There it is (voila), heartless (i) (‘voila’ without ‘i’ = VOLA-), backward (= reverse indicator), the pick of society (elite) for the most part (e) (‘elite’ without ‘e’ = elit = -TILE) (VOLATILE) and highly strung (VOLATILE),
13 Won’t (wont) work (= anagram indicator) (wont = TOWN) with legal aides (CLERKS) (TOWN CLERKS) or officials in The Corporation (TOWN CLERKS),
14 Get lost (get lost! = SCRAM) in Hits from Christmas (‘hits’ from ‘Christmas’ = crmas = SCRAM),
16 They don’t back (OPPOSERS) those who are not the agreeable sort (OPPOSERS),
17 Flower (flower/river Po) raised (= reverse indicator) (Po = OP-) near tub (pot) gets clipped (t) (‘pot’ without ‘t’ = -PO-) on plot (-SITE) (OPPOSITE) on the other side (OPPOSITE),
19 Secure the services of (RETAIN) border’s retail chain (borders ‘RETail chAIN’ = RETAIN),
21 One of those in the abbey (play in The Abbey) needing no introduction (p) (‘play’ without ‘p’ = LAY-) leads monks and nuns (leads ‘Monks And Nuns’ = -MAN) (LAYMAN) and one of the flock (LAYMAN),
23 Sample of the natural gases (sample of the ‘naturAL GAses’ = ALGA) found in seaweed (ALGA),
24 Overturned (= reverse indicator) wagon (dray = YARD) in back garden (YARD).