After first of blunders, game’s completely gone (6)
I believe the answer is:
blotto
'completely gone' is the definition.
(both can mean very drunk)
'after first of blunders game's' is the wordplay.
'after' means one lot of letters go next to another.
'first of blunders' becomes 'b' (1st letter of 'blunders').
'game' becomes 'lotto' (the UK National Lottery).
'b' put next to 'lotto' is 'BLOTTO'.
(Other definitions for blotto that I've seen before include "Get very drunk" , "Cockeyed drunk" , "wrecked" , "Plastered, hammered, sloshed" , "Totally drunk" .)