Islamic ruler (4)
'islamic ruler' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for emir that I've seen before include "Arabic ruler" , "Eastern ruler in mire" , "Arab ruler" , "Title of various rulers; I'm ER (anag.)" , "Ruler or chieftain in Arabia" .)
'islamic ruler' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for caliph that I've seen before include "Sultan of Turkey" , "Harun al-Rashid, say" , "Historical Muslim ruler" , "religious leader" , "Islamic leader" .)