Saying no more. Just filling in the little holes (9,2)

I believe the answer is:

buttoning up

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'saying no more' is the definition.
I can't tell whether this definition defines the answer.

'just filling in the little holes' is the wordplay.
'just' becomes 'but' (I've seen this in other clues).
'filling in the little holes' becomes 'toningup' (I can't justify this - if you can you should give a lot more credence to this answer).
'but'+'toningup'='BUTTONING UP'

Can you help me to learn more?

I've seen this clue in the Evening Standard.

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