Score I put together in game (6-3)
I believe the answer is:
twenty-one
'game' is the definition.
(twenty-one is a kind of game)
'score i put together' is the subsidiary indication.
'score' becomes 'twenty' ('twenty' can be a synonym of 'score'**).
'i' becomes 'one' ('one' can be a synonym of 'i').
'put together' means one lot of letters go next to another.
'twenty'+'one'='twentyone'
'in' is the link.
(Other definitions for twenty-one that I've seen before include "Card game, blackjack or pontoon" , "Target total in blackjack or pontoon" , "XXI - used to be the coming of age year" .)