Eastern ruler said to flourish (6)

I believe the answer is:

sheikh

I'm a little stuck... Click here to teach me more about this clue!

'eastern ruler' is the definition.
'sheikh' can be an answer for 'ruler' (sheikh is a kind of ruler). I am not certain of the 'eastern' bit.

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for sheikh that I've seen before include "Leader of an Arab family" , "Broadcast upset" , "Head of Arab tribe, village etc" , "Leader of an Arab tribe, a Muslim chief" , "Weapons maker" .)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.