Mark of a writer in community, inconclusive (5)
I believe the answer is:
colon
'mark of a writer' is the definition.
(punctuation mark)
'community inconclusive' is the wordplay.
'community' becomes 'colony' (I've seen this before).
'inconclusive' means to remove the last letter.
'colony' with its last letter taken off is 'COLON'.
'in' acts as a link.
(Other definitions for colon that I've seen before include "cash" , "Part of intestines" , "Panama port; part of intestine" , "unit of foreign currency" , "Part of the intestine - punctuation mark" .)