Top man reducing the rise in crime (4)

I believe the answer is:

emir

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'top man' is the definition.
(I've seen this before)

I cannot understand how the rest of the clue works.

(Other definitions for emir that I've seen before include "Title of various rulers; I'm ER (anag.)" , "Title of various Muslim rulers" , "Arab leader" , "Middle-Eastern ruler" , "Islamic title" .)

I've seen this clue in the Evening Standard.

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