Essence of prizewinner's youthful energy to fade (6)
I believe the answer is:
wither
'to fade' is the definition.
(synonyms)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for wither that I've seen before include "Turn dry and shrivelled" , "Atrophy" , "decline" , "Droop, shrivel" , "Lose moisture and die" .)