'Contract' - a card game (7)
I believe the answer is:
abridge
'contract' is the definition.
('abridge' can be a synonym of 'contract')
'a card game' is the wordplay.
'card game' becomes 'bridge' (bridge is a kind of card game).
'a'+'bridge'='ABRIDGE'
(Other definitions for abridge that I've seen before include "Shorten, a book say, without losing the sense" , "Tighten up" , "trim" , "Shorten (eg, text)" , "Abbreviate, contract" .)