After two drinks, this setter's game! (3,5)
I believe the answer is:
gin rummy
'this setter's game' is the definition.
'gin rummy' can be an answer for 'game' (gin rummy is a kind of game). I'm not sure about the 'this setter's' bit.
'after two drinks' is the wordplay.
'two drinks' means two replacements for 'drink'.
'after' says to put letters next to each other.
'drink' becomes 'gin'.
'drink' becomes 'rummy' (I am not sure about this - if you are sure you should believe this answer much more).
'gin' next to 'rummy' is 'GIN RUMMY'.
Can you help me to learn more?
(Other definitions for gin rummy that I've seen before include "Card game" , "cards" .)