King provides measuring device (5)
I believe the answer is:
ruler
I believe this is a double definition.
'king' is the first definition.
(I've seen this before)
'measuring device' is the second definition.
(I've seen this in another clue)
'provides' acts as a link.
(Other definitions for ruler that I've seen before include "Controller" , "Strip used in drawing straight lines" , "Leader - line-drawing aid" , "One exercises dominion" , "Despot perhaps" .)