Something made to measure for emperor (5)
I believe the answer is:
ruler
This clue is a double definition.
'something made to measure' is the first definition.
'emperor' is the second definition.
(thesaurus)
'for' acts as a link.
(Other definitions for ruler that I've seen before include "king perhaps" , "Strip with straight edge to measure" , "Person in authority" , "person holding sway?" , "Chief" .)