Curtail a game (7)
I believe the answer is:
abridge
'curtail' is the definition.
(I've seen this before)
'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" , "Shorten (eg, text)" , "Big read (anag) - shorten text" , "Shorten by using fewer words" , "Concentrate" .)