Son of John and Yoko (4)
I believe the answer is:
sean
'son of john and yoko' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for sean that I've seen before include "guy at Number 10 [IRISHMAN]" , "Penn, Bean or O'Casey" , "Irish form of John" , "- - Connery (007)" .)