Possible Clues:

• Sydney's bored when following only one player in chess club
• Gambler's game, perhaps
• Game that is this puzzle's theme
• Very dirty, sailor in game
• A club - or a spade?
• John may have it in spades, but you may get it in the neck
• Vingt-et-un or a similar card-game
• Great deal?
• One club for the knave of spades?
• Club used in card game