Keep one, no good holding back (9)

I believe the answer is:

retaining

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'holding back' is the definition.
('retain' can be a synonym of 'hold back')

'keep one no good' is the wordplay.
'keep' becomes 'retain' (synonyms).
'one no good' becomes 'ing' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'retain'+'ing'='RETAINING'

Can you help me to learn more?

(Other definitions for retaining that I've seen before include "Hanging on to" , "Holding back in Tangier" .)

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

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