Tory let slip a game of chance (7)
I believe the answer is:
lottery
'a game of chance' is the definition.
(I know that lottery is a type of gambling game)
'tory let slip' is the wordplay.
'slip' indicates anagramming the letters.
'tory'+'let'='torylet'
'torylet' with letters rearranged gives 'LOTTERY'.
(Other definitions for lottery that I've seen before include "Raffle" , "Sweepstake" , "The random drawing of numbers from a drum" , "chancy business" , "Chance process" .)