Essentially one can’t better no-no girl? (7)

I believe the answer is:

nanette

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'no-no girl?' is the definition.
(I've seen this in another clue)

'essentially one can't' is the wordplay.
'essentially' says to take the centre.
'can't' becomes 'anette' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
The middle letter of 'one' is 'n'.
'n'+'anette'='NANETTE'

'better' is the link.
This may not be correct. It may belong to another bit of the clue.

Can you help me to learn more?

(Other definitions for nanette that I've seen before include "Old musical 'No, No .......'" , "Woman" , "No, No, - is Tea for Two musical" , "girl" , "No, No, --, Nineteen-Twenty Five musical" .)

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

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