Frost has written about a potentate (4)
I believe the answer is:
emir
'potentate' is the definition.
(I've seen this in another clue)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for emir that I've seen before include "Islamic title" , "eader abroad?" , "Arab leader" , "Middle-Eastern ruler" , "Muslim chief" .)