Across:
1 Upsetting (= reverse indicator), short (s) fuss ('fuss'= 'ssuf' without 's' = SUF-) from couple (couple/fasten = -FIX) (SUFFIX) producing subscript (subscript = SUFFIX),
4 Creative (ARTISTIC) type from museum (ART-) is (-IS-) getting endless (k) local credit (‘tick’ without ‘k’ = -TIC) (ARTISTIC),
9 The birthplace (CRADLE) of even Orlando (even letters of ‘oRlAnDo’ = -RAD-)? Port (port/left = -L-) in Clare (CE = C-E)! (CRADLE),
10 Has natural ability (INSTINCT) to nose? (INSTINCT),
12 Run down the country (MISGOVERN) to train (= anagram indicator) Virgo’s men (Virgo’s men = MISGOVERN),
13 Fire the imagination (ROUSE) playing (= anagram indicator) Euros (Euros = ROUSE),
14 Sounds like swell of anger between individuals (RAISED VOICES) in States (states/says = VOICES) after (= position indicator) introducing 18 across (introducing ‘raise the flag’ = RAISE-) at start of discussion (start of ‘Discussion’ = -D) (RAISED VOICES),
18 Give the impression the president is at home? (RAISE THE FLAG) Give up! (RAISE THE FLAG),
21 Serves up (= reverse indicator) duck (-O-) covered in wine (port = TR-OP) (TROOP) in company (TROOP),
22 Saves face, for example (EMOLLIENT), of gangster’s lover (-MOLL-) that is (i.e. = -IE-) behind confusion (behind /last letter of ‘confusioN’ = -N-) in Alien (ET = E-T) (EMOLLIENT),
24 Noisy type in car (HORN-) takes channel (-PIPE) (HORNPIPE) to overseas dance (HORNPIPE dance for sailors),
25 The foreign (‘the’ foreign = LA-) investigation (-TEST) (LATEST) reproduced in Vogue (LATEST),
26 Grave (SOMBRE-) exchange of words (row) dismisses women (w) (‘row’ without ‘w’ = -RO) (SOMBRERO) employed by one hiding from The Sun (SOMBRERO),
27 Brought up (RAISED) in 14 across from the start (‘raised voices’ from the start = RAISED).
Down:
1 So creamy (so creamy)? Bananas (= anagram indicator) (so creamy = SYCAMORE) and maple! (maple tree = SYCAMORE),
2 Finishes 18 across (finishes ‘raise the flag’ = FLAG-) and small (-S-) joint (-HIP) (FLAGSHIP) with one of those going overseas with the person running The Fleet (FLAGSHIP carries the commanding admiral),
3 Soldier (GI) returns (= reversal indicator) (GI = IG-) from centre overlooking (centre ‘overLOOking’ = -LOO) (IGLOO) residence way up north (IGLOO),
5 Refuting the idea (RENUNCIATION) and point (compass point East = -E-) by mother (-NUN-) from Channel Islands (-CI-) consumed by allowance (ration = R-ATION) (RENUNCIATION),
6 Cramp (INTERFERE) from reading (one of the 3Rs = -R-) Tenerife (Tenerife) novel (= anagram indicator) (Tenerife = INTE-FERE) outside (INTERFERE),
7 Work out (TONE UP) why she leaves penthouse? (‘she’ leaves ‘penthouse’ = pentou = TONE UP),
8 Caught (C-) by State (-UTTER) (CUTTER) Coastal Patrol Boat (coastal patrol boat = CUTTER),
11 One of those going out a lot (HEAVY SLEEPER) with a Falstaffian character (HEAVY character) from a spy ring (SLEEPER) (HEAVY SLEEPER),
15 Leaving questions (Leaving Cert questions = EXAM PAPER) that could be best answered by those who should have learnt their lessons (EXAM PAPER),
16 Bras from Brussels Lace? (‘bras’ from ‘Brussels lace’ = ussellce = CLUELESS) Had no idea that was possible! (CLUELESS),
17 Disturbed (AGITATED) by advertisement (ad = A-D) about Soldier (-GI-) Museum (-TATE- museum) (AGITATED),
19 Makes a lasting impression (ETCHES) with gags (retches) needing no introduction (r) (‘retches’ without ‘r’ = ETCHES),
20 Foreign Republicans (US Republican Party = Grand Old Party = GOP) recall (= reversal indicator) (GOP = POG-) memory (Read Only Memory = -ROM) (POGROM) of wholesale slaughter (POGROM),
23 Meatballs without best (‘meatballs’ without ‘best’ = maall = LLAMA) type of meat from The Andes? (LLAMA).