Produce firm short undergarment (7)
I believe the answer is:
harvest
'produce' is the definition.
(both can mean products or yield from farming)
'firm short undergarment' is the wordplay.
'firm' becomes 'hard' (both can mean durable or strong).
'short' means to remove the last letter.
'undergarment' becomes 'vest' (vest is a kind of undergarment).
'hard' with its final letter removed is 'har'.
'har'+'vest'='HARVEST'
(Other definitions for harvest that I've seen before include "reap rewards" , "Yield from plants in a single growing season" , "Seasonal yield" , "Crop gathering" , "Cut down" .)