Ancient Egyptian leader upset about demonstration (7)

I believe the answer is:

nomarch

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'ancient egyptian leader' is the definition.
The definition suggests a singular noun which matches the answer.

'upset about demonstration' is the wordplay.
'upset' shows that the letters should be reversed in order.
'about' becomes 'on' (as in a book 'on' a certain topic).
'demonstration' becomes 'march' (type of protest or demonstration).
'on' reversed gives 'no'.
'no'+'march'='NOMARCH'

Can you help me to learn more?

(Other definitions for nomarch that I've seen before include "Greek governor" , "Chief magistrate" .)

I've seen this clue in The Times.

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