No new deal for capital city assistant (4)

I believe the answer is:

aide

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'city assistant' is the definition.
'aide' can be an answer for 'assistant' (I know that aide is a type of gal Friday). I'm not certain of the 'city' bit.

'no new deal for capital' is the wordplay.
'no new deal' becomes 'de' (I am not sure about this - if you are sure you should believe this answer much more).
'for' is a charade indicator (letters next to each other) (I've seen this in other clues).
'capital' becomes 'ai' (resembles 'Ad', old-fashioned term for excellent).
'de' put after 'ai' is 'AIDE'.

Can you help me to learn more?

(Other definitions for aide that I've seen before include "Second" , "Political assistant" , "Right-hand man/woman" , "Helper" , "auxiliary" .)

I've seen this clue in the Sydney Morning Herald.

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