Two-deck card game (7)
I believe the answer is:
canasta
'two-deck card game' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for canasta that I've seen before include "Card game -- as an act (anag)" , "Rummy-like card-game" , "Decorated with artificial jewels" , "Card game of the rummy family" , "Card game like rummy" .)