Musical John (5)
I believe the answer is:
elton
'musical john' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for elton that I've seen before include "..... Jonn (musician)" , "First name of singer/songwriter born Reginald Dwight in 1947" , "Ben --; -- John" , ". . . . . John (musician)" , "Sir - - John, singer songwriter" .)