Moorish sailor's card game (9)
I believe the answer is:
blackjack
'card game' is the definition.
(blackjack is a kind of card game)
'moorish sailor's' is the wordplay.
'moorish' becomes 'black'.
'sailor' becomes 'jack' (I've seen this before).
'black'+'jack'='BLACKJACK'
(Other definitions for blackjack that I've seen before include "2 8 [CASINO GAME]" , "Casino card game" , "Vingt-et-un - pirates' ensign" , "A card game in which the object is to beat the bank" , "Club" .)