Church work by fashionable composer (6)
I believe the answer is:
chopin
'composer' is the definition.
(Frederic Chopin)
'church work by fashionable' is the wordplay.
'church' becomes 'ch' (common abbreviation).
'work' becomes 'op' (common abbreviation for 'opus').
'by' is a charade indicator (letters next to each other).
'fashionable' becomes 'in' (in can mean fashionable or trendy).
'ch'+'op'+'in'='CHOPIN'
(Other definitions for chopin that I've seen before include "Composer of "Tristesse"" , "See 10" , "his writing noted" , "Polish composer of much piano music" , "Polish pianist-composer" .)