Plant genre improves in process (7,8)
I believe the answer is:
evening primrose
'plant' is the definition.
(evening primrose is a kind of plant)
'genre improves in process' is the wordplay.
'process' indicates anagramming the letters.
'genre'+'improves'+'in'='genreimprovesin'
'genreimprovesin' with letters rearranged gives 'EVENING-PRIMROSE'.
(Other definitions for evening primrose that I've seen before include "source of oil" , "flowering plant" , "Herbal remedy" , "type of oil" , "Bloomer" .)