Lift best flipping prize (7)
I believe the answer is:
jackpot
'prize' is the definition.
(I know that jackpot is a type of prize)
'lift best flipping' is the wordplay.
'lift' becomes 'jack' (jacking is a kind of lifting).
'best' becomes 'top' (top can mean the very best).
'flipping' shows that the letters should be reversed in order.
'top' backwards is 'pot'.
'jack'+'pot'='JACKPOT'
(Other definitions for jackpot that I've seen before include "Cumulative prize" , "more than just change for the better" , "Large cash prize" , "Huge gambling prize" , "Accumulated prize" .)