Ancient Mariner's story upset an Arab prince (4)
I believe the answer is:
emir
'arab prince' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for emir that I've seen before include "Top man" , "Muslim chief" , "Islamic title" , "Islamic ruler" , "Arabian ruler" .)