Prize returned by small boxers? (7)
I believe the answer is:
drawers
'boxers?' is the definition.
(boxers are a type of underwear or drawers)
'prize returned by small' is the wordplay.
'prize' becomes 'reward' (a prize may be given as a reward).
'returned' says the letters should be written backwards.
'by' is a charade indicator (letters next to each other).
'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 "Could be a chest of them but they're worn lower down" , "designers" , "Panties" , "Underpants or sketchers" , "Undergarments" .)