1. Green, not unusual (6)
COMMON - double definition.
4. Patriotic tune the man composed (6)
ANTHEM - anagram (composed) of THE MAN.
9. Covered entrance I start to construct in Iberian city (7)
PORTICO - I (I) and (C)onstruct inside Iberian city (PORTO).
10. European city, wind consuming one (5)
TURIN - wind (TURN) consuming one (I).
11. Plant in rather isolated situation, initially (4)
IRIS - (I)n (R)ather (I)solated (S)ituation.
12. Fashionable attitude, for example (8)
INSTANCE - fashionable (IN), attitude (STANCE).
14. Funny bone providing gentle stimulation (3-8)
RIB-TICKLING - bone (RIB), providing gentle stimulation (TICKLING).
18. Reference a couple of pages, then conclude with nine (8)
APPENDIX - a (A), couple of pages (PP), conclude (END), nine (IX).
20. Feeling of irritation in suit, chafing (4)
ITCH - in su(IT CH)afing.
22. Animal taking a promenade back (5)
LLAMA - well, it had to be llama - and it was! A (A), promenade (MALL) backwards. On looking up I realise I’d never known this meaning of mall and thus not realised the origins of the American shopping mall. Mall - a shaded avenue especially one open to the public. Hence 'The Mall' in London but not Pall Mall which was named after a ball game played there during the 17th century presumably with mall-ets - mall in US being another word for mallet.
23. Strangely, nude art not valued (7)
UNRATED - anagram (strangely) of NUDE ART.
24. In net, dry rocks (6)
TRENDY - anagram (rocks) of NET DRY.
25. Diggers loading ship with stuff heading for Estonia (6)
SPADES - inside (loading) ship (SS) is stuff (PAD) and (E)stonia.
1. Originally charging ahead, draw game (3,3)
CUP TIE - (C)harging, ahead (UP), draw (TIE).
2. Drink in vermouth sheepish male served up (7)
MARTINI - in (IN), vermouth (IT - a common crossword term - think gin and it where 'it' stands for ITalian vermouth), sheepish male (RAM) all served upwards.
3. God having some good intentions (4)
ODIN - some go(OD IN)tentions. Odin is associated with, well, pretty much everything - wisdom, healing, death, royalty, the gallows, knowledge, war, battle, victory, sorcery, poetry, frenzy, and the runic alphabet, and is the husband of the goddess Frigg.
5. You're welcome, never! (3,2,3)
NOT AT ALL - double definition.
6. Ben riding chariot over great lake (5)
HURON - Ben-(HUR) the 1959 film, over (ON).
7. Day important for primate (6)
MONKEY - day (MONday), important (KEY).
8. Couple I snubbed, one of fifty in the US (11)
CONNECTICUT - couple (connect), I (I), snubbed (CUT). I think my problems came from not believing that 'one of 50' in the US would be a particular state - well, not for a long time.
13. Normal position on a road (8)
STANDARD - position (STAND) a (A), road (RD).
15. Introducing gallery, sign marked (7)
NOTATED - inserting (introducing) gallery (TATE) into sign (NOD).
16. Speculation about everyone dancing (6)
BALLET - speculation (BET) about everyone (ALL).
17. Island ways verbalised (6)
RHODES - homophone (verbalised) of roads.
19. Reportedly unattractive flier (5)
PLANE - homophone of plain.
21. Catch constituent up (4)
TRAP - constituent (PART) upwards.