Veg, not quite enough for a feast (4)
I believe the answer is:
bean
'veg' is the definition.
(bean is a type of vegetable)
'not quite enough for a feast' is the wordplay.
'not quite enough for' means to remove the last letter (most but not all of the letters).
'a feast' becomes 'beano' (I've seen this before).
'beano' with its last letter removed is 'BEAN'.
(Other definitions for bean that I've seen before include "Haricot or runner?" , "Seed of e.g. coffee" , "Seed of coffee plant" , "Seed; head" , "Broad, French or kidney?" .)