Reduces the strength of stoats following; sound so lost (10)

I believe the answer is:

undermines

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'reduces the strength' is the definition.
I can't tell whether this defines the answer.

'stoats following sound so lost' is the wordplay.
'stoats' becomes 'ermines' (I've seen this in another clue).
'following' means one lot of letters go next to another.
'lost' indicates named letters should be taken away.
'sound' with 'so' taken away is 'und'.
'ermines' put after 'und' is 'UNDERMINES'.

'of' acts as a link.

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

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