A prize being wasted (7)

I believe the answer is:

atrophy

I'm a little stuck... Click here to teach me more about this clue!

'a prize being wasted' is the definition.
I can't tell whether this definition defines the answer.

'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 "Become weak and die away through lack of use" , "shrivel" , "Degeneration" , "Decay" , "Waste away as through lack of food" .)

I've seen this clue in The Guardian.

Want a hint initially instead of a full solution? Install my app