Turn to a bigger prize (8)
I believe the answer is:
rollover
'a bigger prize' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'turn to' is the wordplay.
'turn' becomes 'roll' (roll is a kind of turn).
'to' becomes 'over' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'roll'+'over'='ROLLOVER'
Can you help me to learn more?
(Other definitions for rollover that I've seen before include "A carrying on of a lottery prize to the next draw" , "big lottery prize" , "Be easily defeated" , "deferred payment" , "Multiple-week jackpot" .)