Title of various Muslim rulers (4)
I believe the answer is:
emir
'title of various muslim rulers' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for emir that I've seen before include "Ruler or chieftain in Arabia" , "Arab leader" , "Title of various Muslim rulers" , "Ruler in the Middle East and mire" , "Islamic title" .)