### Clue: George Best with a harp mysteriously appears in Gay musical (3,7,5)
### Answer: THE BEGGAR’S OPERA 
 ### Explanation: Definition: Gay musical
  **Anagram of**(mysteriously appears) [GEORGE BEST **plus**(with) A HARP]
Answer: A ballad opera,musical written by John Gay in 1728.  It has had many adaptations, including a German one.