Vegetable makes fellow leave (9)
I believe the answer is:
mangetout
'vegetable' is the definition.
(I've seen this before)
'fellow leave' is the wordplay.
'fellow' becomes 'man' (fellow can mean a man).
'leave' becomes 'getout' (getting out is a kind of leaving).
'man'+'getout'='MANGETOUT'
'makes' is the link.
(Other definitions for mangetout that I've seen before include "something on the plate" , "Type of pea" , "Sugar peas" , "Edible pea pods" , "vegetables" .)