Pontoon score sounded even (6-3)
I believe the answer is:
twenty-one
'pontoon' is the definition.
(names for the same card game)
'score sounded even' is the wordplay.
'score' becomes 'twenty' (synonyms).
'even' means one should take alternating letters (even-numbered letters are used).
The alternate letters of 'sounded' are 'one'.
'twenty'+'one'='TWENTY-ONE'
(Other definitions for twenty-one that I've seen before include "Target total in blackjack or pontoon" , "XXI - used to be the coming of age year" , "Card game, blackjack or pontoon" .)