Clue: Maybe Marvin, backed by a couple of unknowns, imbibing god-king's cocktail (5,5)
Answer: HANKY PANKY
Explanation: Definition: cocktail

**HANK** ("maybe Marvin") *backed by* **Y** + **Y** ("a couple of unknowns") *imbibing* **PAN** ("god") +** K** (king)