Clue: Some lad with the cunning to bank unspecified amount in poker (5,4,2)
Answer: TEXAS HOLD ‘EM
Explanation: Definition: poker
An envelope ('to bank') of X ('unspecified amount') in TEASHOLDEM, an anagram ('cunning') of 'some lad' plus 'the', for a variety of the card game poker in which each player has two cards, forming the best five card hand with any three of five cards common to all the players.