1: Artist back on the issue of causing inflamation. (5)
4: Arcking shot from Bill O'Brien (3)
9: Think at length about lost planet, comet (11)
10: Bumped into yours truly at junction (3).
11: Green coat for Italian composer and Spanish painter (9)
12: Content little rest for the painter (5)
13: Later round without an opponent (3)
14: Regains no recollection from thinking (9)
16: Standard cart coming back with jam (9)
17: Going after the final piece of puzzle for a very long time (3)
18: Belgian port getting rid of an idiot (5)
20: Love to influence the polar type. (9)
23: Provoke Church of Scotland's absent leader (3)
24: Cereal vermin seized by superb 16-down (11)
25: Handle two-thirds of the world (5)
27: Authority, for example (sic) (3-2)