Boy king of Egypt (3)
I believe the answer is:
tut
'boy king of egypt' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tut that I've seen before include "King wrapped up" , "Annoyed exclamation" , "Noise of disapproval" , "Disapproving comment" , "Express disapproval" .)