Superman's alias (4)
I believe the answer is:
kent
'superman's alias' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for kent that I've seen before include "County of SE England" , "County; punting pole" , "Lear's faithful Earl" , "Garden of England - Superman's family name" , "Part of 1 25 [KING LEAR]" .)