Move that shortens the game a little? (6)
I believe the answer is:
gambit
'move' is the definition.
(I know that gambit is a type of chess move)
'shortens the game a little?' is the wordplay.
'shortens' means to remove the last letter (I've seen 'shortened' mean this).
'a little?' becomes 'bit' (both can mean a small amount of something).
'game' with its last letter removed is 'gam'.
'gam'+'bit'='GAMBIT'
'that' acts as a link.
(Other definitions for gambit that I've seen before include "Opening ploy in chess" , "Opening sacrifice made in chess game" , "Sacrificial chess opening" , "Opening move to gain advantage" , "Sacrificial strategy in chess" .)