Waste away winning a prize (7)
I believe the answer is:
atrophy
'waste away winning' is the definition.
'atrophy' can be an answer for 'waste' (atrophy means to waste away). I'm unsure of the 'away winning' bit.
'a prize' is the wordplay.
'prize' becomes 'trophy' (synonyms).
'a'+'trophy'='ATROPHY'
Can you help me to learn more?
(Other definitions for atrophy that I've seen before include "Waste away - sounds like a sporting award" , "Waste away as through lack of food" , "Waste away through under-nourishment or lack of use" , "wasting away" , "shrivel" .)