Across:
8 One of those damaging material (VANDAL) in The British Museum (Victoria and Albert = V AND A = VANDA-) gets jail in the end (‘jaiL’ in the end = -L) (VANDAL),
9 Wild (= anagram indicator) ostrich (ostrich = HISTOR-C) roaming around one (-I-) (HISTORIC) landmark (HISTORIC),
10 Some Montevideo bohemian (some ‘montevidEO BOhemian’ = eobo) takes up (= reverse indicator) (eobo = OBOE) instrument (OBOE),
11 Breda’s relative in Holland perhaps (DUTCH UNCLE from Breda a city in Holland) offers critical advice to the US House (in US, person giving critical advice perhaps = DUTCH UNCLE),
12 Turns up (= reverse indicator), for example (e.g. = -GE), to study (den = -N ED -) at Oxford (O-) (ON EDGE), a bundle of nerves (ON EDGE),
14 Support (STAY) from The House (HOME) (STAY HOME) to leave the work to others perhaps (STAY HOME),
15 It’s gas (CARBON) leaving Mark out in the snow (mark in the snow FOOTPRINT) (CARBON FOOTPRINT) and that’s noted by The Greens! (CARBON FOOTPRINT),
18 Fools (cons = C-ONS) consuming most of (e) the course (route) (‘route’ without ‘e’ = -ROUT-) (CROUTONS) of baked bread cut in cubes (CROUTONS),
20 Stargazer lose rag (‘stargazer’ loses ‘rag’ = stazer = ERSATZ), as it’s not as good as the real thing (ERSATZ),
22 Stoned (HIGH) eccentric (= anagram indicator) trips (trips = PRI-ST) around Spain (-E-) (HIGH PRIEST) with leader of cult (HIGH PRIEST),
24 The Fringe’s live stream (the fringes ‘Live streAM’ = liam) sends up (= reverse indicator) (liam = MAIL) The Post (MAIL),
25 It’s found in some sherries (yeast on the surface of dry Fino sherries = FLOR-) cherished by university students (firsts = 1sts = -ISTS) (FLORISTS) produced by those selling Rosés (roses)? (FLORISTS),
26 Models (models) show off (= anagram indicator) (models = SELDOM) on rare occasions (SELDOM).
Down:
1 Copy (CARBON) opened by 15 across (opened by ‘carbon footprint’ = CARBON),
2 Is not working (IDLE) for the papers (ID- papers) long (-L-) – what’s the point? (compass point East = -E) (IDLE),
3 Station boss (Director General of RTE = -DG-) detained in Down (blue = BLU-E-) at broadcast (-ON) (BLUDGEON) from club (club/beat = BLUDGEON),
4 Characters with no carers (‘characters’ with no ‘carers’ = hact = CHAT) or that’s the talk online (CHAT),
5 Condition (ASTHMA) of a (A-) street (-ST-) close to Howth (close/end to ‘Howth’ = -H-) around marina (around ‘MarinA’ = -MA) (ASTHMA),
6 Those generating a lot of interest (LOAN SHARKS) in the starters of antipasti – namely, salami hams (starters ‘Of Antipasti Namely Salami Hams’ = -oansh = -OAN SH-) found in Early Birds (larks = L- -ARKS) (LOAN SHARKS),
7 Firemen (firemen) working (= anagram indicator) (firemen = RIF-EMEN) around central Ireland (central ‘ireLand’ = -L-) (RIFLEMEN) – are they the ones in the firing line? (RIFLEMEN),
13 A cheery Dub (a cheery Dub) playing (= anagram indicator) (a cheery Dub = DEBAUCHERY) with lack or morals (DEBAUCHERY),
14 Small (S-) gardening tools (-HOES) (SHOES) – essential, regardless of the surface underfoot (SHOES),
6 Frailer (frailer) boss (= anagram indicator) (frailer = A-R RIFLE) holding his heart (‘his’ heart = -I-) (AIR RIFLE) carried by one of those in 7 down, for example (AIR RIFLE carried by ‘riflemen’),
17 Nurse (TREAT-) is (-IS-) taking direction (East = -E) (TREATISE) from written study (TREATISE),
19 Sudden surge? (ONRUSH) Get diver out of Hudson River! (get ‘diver’ out of ‘Hudson River’ = husonr = ONRUSH),
21 Morality dismissing my (‘morality’ dismissing ‘my’ = oralit = TAILOR) Man of the Cloth? (TAILOR),
23 Borders of Easter Daisy (Borders of ‘EAster DaiSY’ = EASY) required little effort (EASY),
24 Sicilian neighbour’s (Malta) short? A (a) (‘malta’ without ‘a’ = MALT) type of whisky! (MALT whisky).