Across:
8 Take a long look (GAZE-) for best offer (Best Offer = -BO) (GAZEBO) for summerhouse (GAZEBO),
9 Jockey (HORSEMAN) sounds (= homophone indicator) gruff (‘hoarse’ = ‘horse’ = HORSE-) to staff (-MAN) (HORSEMAN),
10 Found up (= reverse indicator) in Kolkata obscured (in ‘kolkaTA OBscured’ = taob = BOAT) by oriental junk? (junk/flat bottomed Chinese BOAT),
11 Wise guys (MAGI-) from Chicago head (‘Chicago’ head = -C) to Washington (WA-) for a fair amount of (half of) rounds (half of ‘rouNDS’ -NDS) (MAGIC WANDS) in bewitching bars (MAGIC WANDS),
12 Macmillan has no Mam (‘Macmillan’ has no ‘Mam’ = cillan = CALL IN) to visit (CALL IN),
14 Banker is (banker is) confused (= anagram indicator) (banker is = BREAK-INS) by robberies (BREAK-INS),
15 Observe Status Quo (DON’T ROCK THE BOAT) and fellow (DON -) tenor (-T) from 24 across (‘rock’ = ROCK) and most of (m) them (them) (‘them’ without ‘m’ = THE) from 10 across (‘boat’ = BOAT) (DON’T ROCK THE BOAT),
18 Miraculously gets rid of oily (‘miraculously’ removes ‘oily’ = mraculus = MUSCULAR) beefy type (MUSCULAR),
20 The odd germ (the odd ‘GeRm’ = GR-) on a piece of cake (piece of cake = -EASY) (GREASY) from a type of spoon (GREASY spoon),
22 One preaching (SERMONISER) to Yank (= anagram indicator) – remorse (remorse = SERMO-ER) is all about sin (sin) in retrospect (= reverse indicator) (sin = -NIS-) (SERMONISER),
24 Playback (= reverse indicator) covered Limerick/Cork (covered by ‘limericK CORk’ = kcor = ROCK) type of music (ROCK),
25 A (A-) European (Serb) loses the head (s) (‘Serb’ without ‘s’ = -ERB-) in Paris, for instance (city = -C-ITY) (ACERBITY), out of bitterness, in a manner of speaking (ACERBITY),
26 Man in the street losing interest (‘man in the street’ losing ‘interest’ = manhte = ANTHEM) in country music (ANTHEM).
Down:
1 Knocked back (= reverse indicator) sample of Burkina Faso masala (sample of 'burkina fASO MASala' = asomas = SAMOSA) for sale in Indian food market (SAMOSA),
2 Aromas from Sacramento (‘aromas’ from ‘Sacramento’ = cent = CENT) – the capital (capital/money = CENT),
3 Butterfly (COMMA- butterfly) is named (-N-) by Trim (d) academic (Don) (‘don’ without ‘n’ = -DO) (COMMANDO) – the one recruited for The Missions (COMMANDO),
4 Bully boy (THUG) gets time (T-) to show some affection (-HUG) (THUG),
5 Credit (CR-) European Commission (-EC-) and His Eminence (His Eminence = -HE) (CRECHE) for looking after the little ones (CRECHE),
6 Extraordinary (REMARKABLE) state (REMARK-) on rebellious (= reverse indicator) small island in the Mediterranean (Elba = -ABLE) (REMARKABLE),
7 A reading (a reading) adapted (= anagram indicator) (a reading = GARDENIA) by Jasmine from The Cape? (Cape jasmine = GARDENIA),
13 Some cartel (some cartel) unsettled (= anagram indicator) (some cartel = LATECOMERS) by those missing things kicking off (LATECOMERS),
14 Break the ice dismissing Hecate (‘break the ice’ dismissing ‘Hecate’ = breki = BIKER) – presumably she’s a member of the Hells Angels? (BIKER),
16 Ugly (= anagram indicator) coup (coup = OPU-C-) takes in the French (‘the’ French = -LE-) Nationalist (-N-) going to Spain (-E) (OPULENCE) with great wealth (OPULENCE),
17 Moralist’s view (HIGH ROAD) of the mountain pass (HIGH ROAD),
19 Pulse (LENTIL) bean removed from table linen (‘bean’ removed from ‘table linen’ = LENTIL),
21 Jack (SOCKET) Argyle (Argyle SOCK-) and Lawrence (TE Lawrence = TE) Back (= reversal indicator) (TE = -ET) (SOCKET),
23 Designer’s concern (style) – without top labels (top ‘Labels’ = l) (‘style’ without ‘l’ = STYE) this is an eyesore (STYE),
24 Mechanical repetition (ROTE) of some backfiring (= reverse indicator) Bangalore torpedoes (some backfiring ‘bangalorE TORpedoes’ = etor = ROTE).