Prize picked up -- small underwear (7)
I believe the answer is:
drawers
'underwear' is the definition.
'prize picked up small' is the wordplay.
'prize' becomes 'reward' (I've seen this before).
'picked up' is a reversal indicator.
'small' becomes 's' (abbreviation - e.g. clothes size).
'reward' written backwards gives 'drawer'.
'drawer'+'s'='DRAWERS'
(Other definitions for drawers that I've seen before include "designers" , "undergarment" , "Underwear (for artists?)" , "Knickers" , "pants" .)