A game involving packs (7)
I believe the answer is:
canasta
'a game' is the definition.
(canasta is a kind of game)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for canasta that I've seen before include "Card game resembling rummy" , "Form of rummy using two decks of cards and four jokers" , "this needs two packs" , "Card-game played with two packs of cards" , "Decorated with artificial jewels" .)