Crossword Genius

Maintains mother doesn't say a word (5,3)

Ross

I believe the answer is:

keeps mum

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'doesn't say a word' is the definition.
I can't judge whether this definition defines the answer.

'maintains mother' is the wordplay.
'maintains' becomes 'keeps' ('keep' can be a synonym of 'maintain').
'mother' becomes 'mum' (informal term for mother).
'keeps'+'mum'='KEEPS MUM'

Can you help me to learn more?

(Other definitions for keeps mum that I've seen before include "If one behaves filially thus" , "stays silent" .)

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