Qatari ruler (4)
I believe the answer is:
emir
'qatari ruler' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for emir that I've seen before include "leader in the East" , "Muslim chief" , "Ruler in the Middle East and mire" , "Title of various rulers; I'm ER (anag.)" , "Islamic title" .)