Former City CEO, perhaps (4)

I believe the answer is:

exec

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

'former city ceo' is the definition.
'exec' can be an answer for 'ceo' (I've seen this in another clue). I am not certain of the 'former city' bit.

I can't explain the remainder of the clue.

Can you help me to learn more?

(Other definitions for exec that I've seen before include "Business manager (abbrev.)" , "Senior manager (abbr)" , "high-flier" , "Senior businessperson (abbr)" , "Businessman" .)

I've seen this clue in The Times.

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