Hammered losing first game (5)
I believe the answer is:
lotto
'game' is the definition.
(the UK National Lottery)
'hammered losing first' is the wordplay.
'hammered' becomes 'blotto' (I've seen this before).
'losing first' means to remove the first letter.
'blotto' with its first letter taken off is 'LOTTO'.
(Other definitions for lotto that I've seen before include "Game of chance similar to bingo" , "Children's game similar to bingo" , "Prize draw" , "Game of chance based on numbered balls being drawn at random" , "house" .)