Sheik's peer (4)
(Other definitions for agha that I've seen before include "Alternative spelling for a Turkish commander" , "Turkish civil or military leader" , "Ruler" , "Turkish officer" .)
'sheik's peer' 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 "Title of various Muslim rulers" , "Middle Eastern ruler" , "Arabic ruler" , "Eastern ruler in mire" , "Eastern chieftain" .)