Shorten a game (7)
I believe the answer is:
abridge
'shorten' is the definition.
(synonyms)
'a game' is the wordplay.
'game' becomes 'bridge' (card game).
'a'+'bridge'='ABRIDGE'
(Other definitions for abridge that I've seen before include "Make shorter in brigade" , "Make a precis of" , "Abbreviate, contract" , "Crop" , "Make shorter, book say" .)