Artist in Somme trench, virtually? (6)
I believe the answer is:
warhol
'artist' is the definition.
(Andy Warhol)
'somme trench virtually?' is the wordplay.
'somme trench' becomes 'war hole'.
'virtually?' means to remove the last letter (all but the last letter).
'warhole' with its final letter taken away is 'WARHOL'.
'in' acts as a link.
(Other definitions for warhol that I've seen before include "- Fisher (B. Potter)" , "Andy ---, pop artist" , "Andy ... modernist artist" , "Modern artist" , "Andy -; he said 'In the future everyone will be famous for fifteen minutes'" .)