A prize for wasting? (7)
I believe the answer is:
atrophy
'wasting?' is the definition.
(I know that wasting can be written as atrophy)
'a prize' is the wordplay.
'prize' becomes 'trophy' (synonyms).
'a'+'trophy'='ATROPHY'
'for' acts as a link.
(Other definitions for atrophy that I've seen before include "Waste away (from disuse?)" , "Decline" , "wasting away" , "Waste away, wither" , "Become weak and die away through lack of use" .)