Less coarse (5)
I believe the answer is:
finer
'less coarse' is the definition.
('fine' can be the opposite of 'coarse' so perhaps 'finer' is reasonable for 'less coarse')
This is all the clue.
(Other definitions for finer that I've seen before include "Better; more slender" , "Of higher quality" , "Better quality" , "More gossamer or splendid" , "More thin, excellent" .)