Writer of features, say, is taking part (8)
I believe the answer is:
essayist
'writer' is the definition.
(I know that essayist is a type of writer)
'features say is taking part' is the wordplay.
'part' indicates a hidden word.
'ESSAYIST' is hidden within 'features say is taking'.
'of' acts as a link.
(Other definitions for essayist that I've seen before include "Writer of short literary pieces" , "One who writes short pieces on given subject" , "Writer of pieces on various subjects" , "Writer of short compositions" , "Lamb, for example" .)