Knave gets trophy and big winnings (7)
I believe the answer is:
jackpot
'big winnings' is the definition.
(a large prize amount)
'knave gets trophy' is the wordplay.
'knave' becomes 'jack' (synonyms).
'gets' says to put letters next to each other.
'trophy' becomes 'pot' (type of trophy).
'jack'+'pot'='JACKPOT'
'and' acts as a link.
(Other definitions for jackpot that I've seen before include "pool" , "best prize!" , "Big win from one-arm bandit" , "major win" , "Large cash prize" .)