### Clue: Fifty hosted by wonderful boy, full house on the cards? (5,4)
### Answer: GRAND SLAM 
 ### Explanation: Definition: full house on the cards
An envlope ('hosted by') of L ('fifty', Roman numeral) in Grand ('wonderful') plus SAM ('boy'). The definition borrows a term from poker, and applies it to the bridge deal in which the declarer takes all the tricks.