Call for a young man in uniform (4)
I believe the answer is:
page
I believe this is a double definition.
'call for' is the first definition.
(to page is to call with a pager)
'a young man in uniform' is the second definition.
(type of royal attendant)
(Other definitions for page that I've seen before include "Piece of paper for a young attendant" , "Boy attendant; send out call for" , "Boy at wedding" , "Leaf of book etc" , "lad wanted to run errands" .)