Across:
8 Auden (Auden = DANU-E) adaptation (= anagram indicator) about British (-B-) (DANUBE) flower (flower/river DANUBE),
9 Guy (guy/male = HE-) Henry is central (‘heNry’ is central = -N) to absurd (= anagram indicator) thing (thing = NIGHT) (HEN NIGHT) for women only (HEN NIGHT),
10 Heads on Irish beer in saloon (heads on ‘Irish Beer In Saloon’ = IBIS) produced by flighty type (IBIS),
11 Two American cities (LA+WA= LAW-A-) offering at auction (bidding) missing diamonds (d) (‘bidding’ without ‘d’ = -BIDING) (LAW-ABIDING) without committing offence (LAW-ABIDING),
12 Sounds like someone’s crying (BOOHOO), as short (k) novel (‘book’ without ‘k’ = BOO-) by one of the American gang (hood) isn’t finished (‘hood’ without ‘d’ = -HOO) (BOOHOO),
14 Exposes (UNEARTHS) setting (= anagram indicator) sun (sun = UN-S) going around our planet (-EARTH-) (UNEARTHS),
15 Look who just walked in (SPEAK OF THE DEVIL) to gossip about the man downstairs (SPEAK OF THE DEVIL),
18 100 (C-) Frenchmen (Messieurs = -MM-) in supply (= anagram indicator) route (route = -O-UTER) (COMMUTER) travelling to work (COMMUTER),
20 Appointment (POST-) in hospital (-ER) (POSTER) for blogger (blogger / POSTER),
22 Leaves for salad lunch (SWISS CHARD) with short (e) clever type (wise) (‘wise’ without ‘e’ = -WIS-) in boat (S-S) club (C-) – and that’s not easy? (-HARD) (SWISS CHARD)
24 Spotted (EYED) in The Observer (EYE-) by 500 (Roman numeral 500 = -D) (EYED),
25 Upper-class (upper-class = U-) woman (-SHE-) from syndicate (-RING) (USHERING) working as an escort (USHERING),
26 Nervous (= anagram indicator) yatter (yatter = TREATY) follows a conflict (TREATY).
Down:
1 Most of (r) the bar (most of the ‘bar’ = BA-) is open-minded (open ‘Minded’ = -M-) to half of 12 across (half of ‘BOOhoo’ = -BOO) (BAMBOO) offering grass (BAMBOO),
2 Much ado about nothing (FUSS) in part of US Senate (part ‘oF US Senate’ = FUSS),
3 Affluent (WELL-TO-DO) women (W-) left (-L-) in Toledo (Toledo = -EL-TO-DO) all over the place (= anagram indicator) (WELL-TO-DO),
4 Who’s (whos = SHOW) out (= anagram indicator) to demonstrate the truth of something? (SHOW),
5 Lacking the skill (UNABLE) in New Labour to dismiss row (‘New Labour’ to dismiss ‘row’ = nelabu = UNABLE),
6 More savage than (WILDER-) the monster (Loch -NESS monster) (WILDERNESS) in The Waste Land (WILDERNESS),
7 Old ruler (SHA-H-) swallows newly opened (‘Newly’ opened = -N-) grand (-G-), first-class (-AI) (SHANGHAI) port in China (SHANGHAI),
13 In principle (‘principle’ = ‘principal’ = HEADMASTER), to the audience (= homophone indicator), it could be Freud? (psychoanalyst / head master? = HEADMASTER),
14 One of those fat types (butter) loses head (b) (‘butter’ loses ‘b’ = UTTER) with Express? (express = UTTER),
16 Trim (p) rugby player (‘prop’ without ‘p’ = PRO -) starts 22 across (starts ‘swiss chard’ = SWISS) (PRO-SWISS) in favour of Alpine country (PRO-SWISS),
17 Hurry through (EXPEDITE) exercise (-PE-) for director (-D-) in Gate (gate = EX-IT-) finale – it’s the ultimate (‘finalE’ it’s the ultimate = -E) (EXPEDITE),
19 Architect releases her (‘architect’ releases ‘her’ = acitct = TACTIC) plan (TACTIC),
21 Big social gatherings (EVENTS) in 24 down (‘even’ = EVEN-) for leaders on Times Square (leaders on ‘Times Square’ = -TS) (EVENTS),
23 Some of the natural gases (some of the ‘naturAL GAses’ = ALGA) found in seaweed (ALGA),
24 Every man takes off army (‘every man’ takes off ‘army’ = even = EVEN) uniform (EVEN).