Across:
1 Sutherland dismisses nuts (‘Sutherland’ dismisses ‘nuts’ = herlad = HERALD) in the paper (HERALD newspaper),
4 She ruins (she ruins = USHERS IN) smashing (= anagram indicator) welcomes (USHERS IN),
9 No Asians in San Sebastian (no ‘Asians’ in ‘San Sebastian’ = nebast = ABSENT) on holiday (ABSENT),
10 Cast a spell over (put into a trance/beguile = ENTRANCE) writer (pen) heading off (p) (“pen” without “p” = EN-) from state down under perhaps? (-TRANCE) (ENTRANCE),
12 Two men (Louis + Ian = LOUIS + IAN-) with a (-A) (LOUISIANA) Texas neighbour (LOUISIANA),
13 Arabian (HORSE) removes museum from summer house (removes ‘museum’ from ‘summer house’ = rhose = HORSE),
14 Bread (MONEY-) and port (port/left = -L-) is a concern for the author (-ENDING) (MONEYLENDING) working in the banking business (MONEYLENDING),
18 Insulting recently divorced partner (PARTING SHOTS) with drinks before closing time (PARTING SHOTS),
21 Most (e) of The (‘the’ without ‘e’ = TH-) Sting (sting/rip off = -ROB) (THROB) is a pain in the face (THROB),
22 Has to have (NEEDS) grape juice (MUST) (NEEDS MUST) and it’s unavoidable (NEEDS MUST),
24 Tudor (Tudor = OUTD-R-) settlement (= anagram indicator) around old (-O-) order (-O-) and school (-S) (OUTDOORS) with open space (OUTDOORS),
25 Spot for a yacht (MARINA) crew getting away from Crimean War (‘crew’ getting away from ‘Crimean War’ = imanar = MARINA),
26 Left (L-) individual (-ONE-) with a handful of (-SOME) (LONESOME) missing people (LONESOME),
27 Spies (AGENTS) American (A-) reporting (= homophone indicator) Lou (“Lou” = “loo” = -GENTS) (AGENTS).
Down:
1 Held a map (held a map = HEADLAMP) out (= anagram indicator) helping the viewer to see in the dark (HEADLAMP),
2 Saving (RESCUING) for fancy (= anagram indicator) nice rugs (nice rugs = RESCUING),
3 Advances (LENDS) far away from Flanders (‘far’ away from ‘Flanders’ = lndes = LENDS),
5 Paper (SUN- newspaper) on D-Day (dday = -DAY D-) rubbished (= anagram indicator) by wrongdoer (sinner) starting off (s) (‘sinner’ without ‘s’ = -INNER) (SUNDAY DINNER) the weekly roast (SUNDAY DINNER),
6 Arrange (= anagram indicator) a horse pen (a horse pen = EARPHONES) with listening devices (EARPHONES),
7 School (S-) admission (-ENTRY) (SENTRY) is the one to watch (SENTRY),
8 State (= homophone indicator) did a job for the bakers (“kneaded” = “NEEDED”) when it was required (NEEDED),
11 Lose it (HAVE A TANTRUM) in rave (HAVE A TANTRUM),
15 Annuals (YEARBOOKS), for example, for 1983 (YEAR-), 1984 (George Orwell’s 1984 = BOOK-) and for the end of the 1990s (for the end of the ‘1990s’ = -S) (YEARBOOKS),
16 The answer (SOLUTION) is in the clue? (SOLUTION),
17 Satyr has (Satyr has = ASHTRAYS) trouble (= anagram indicator) with those holding onto the remnants of the camels (those holding onto the remnants of the Camels/cigarettes = ASHTRAYS),
19 Small (S-) type of bridge (-T-OLL bridge) over river (-R-) (STROLL) is perfect for those going a short distance (STROLL),
20 Town crier loses row (‘town crier’ loses ‘row’ = tncrie = CRETIN) with local idiot (CRETIN),
23 Bad language perhaps (SLANG), in a manner of speaking (SLANG).