Bishop leaves drunk for game (5)
I believe the answer is:
lotto
'for game' is the definition.
(the UK National Lottery)
'bishop leaves drunk' is the wordplay.
'bishop' becomes 'B' (chess abbreviation).
'leaves' suggests deleting specific letters.
'drunk' becomes 'blotto' (slang term).
'blotto' with 'b' taken away is 'LOTTO'.
(Other definitions for lotto that I've seen before include "form of gambling" , "Children's game similar to bingo" , "Game of chance involving balls" , "Game like bingo" , "house" .)