Penn of "Milk” (4)
I believe the answer is:
sean
'penn of milk' 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 "- - Connery (007)" , "guy at Number 10 [IRISHMAN]" , "Irish form of John" , "Penn, Bean or O'Casey" .)