John —, Beatle (6)
I believe the answer is:
lennon
This clue is a double definition.
'john' is the first definition.
(I've seen this before)
'beatle' is the second definition.
(I've seen this before)
(Other definitions for lennon that I've seen before include "old pop star" , "John -, musician murdered nineteen eighty" , "Beatle airport" , "Member of the Beatles, d.1980" , "John - (Imagine)" .)