Game on the snooker table? (3)

I believe the answer is:

nap

I'm a little stuck... Click here to teach me more about this clue!

'game' is the definition.
(card game)

I don't understand the rest of the clue.

(Other definitions for nap that I've seen before include "Pile (on e.g. velvet)" , "One likely to win" , "A daytime doze" , "Take forty winks" , "A brief snooze" .)

I've seen this clue in the Evening Standard.

Want a hint initially instead of a full solution? Install my app