Dictator's a pure and simple ruler in the Gulf (5)

I believe the answer is:

ameer

'ruler in the gulf' is the definition.
(several Gulf rulers are titled emir or ameer)

I don't understand how the remainder of the clue works.

(Other definitions for ameer that I've seen before include "Former ruler's title in Afghanistan" , "Asian dignitary" , "Muslim prince (alt.spelling)" , "foreign ruler" , "Muslim prince's title" .)

I've seen this clue in The Guardian.

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