Waste away, having won a cup (7)
I believe the answer is:
atrophy
'waste away' is the definition.
(I've seen this in another clue)
'a cup' is the wordplay.
'cup' becomes 'trophy' (I've seen this before).
'a'+'trophy'='ATROPHY'
'having won' is the link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for atrophy that I've seen before include "Become weak and die away through lack of use" , "Waste away through under-nourishment or lack of use" , "Decline" , "Decay" , "Waste away - sounds like a sporting award" .)