They're used for cleaning badly rusted bearing (7)

I believe the answer is:

dusters

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'they're used for cleaning' is the definition.
The definition suggests an adverb but the answer is not.

'badly rusted bearing' is the wordplay.
'badly' is an anagram indicator (letters in the wrong order).
'bearing' becomes 's'.
'rusted' anagrammed gives 'duster'.
'duster'+'s'='DUSTERS'

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I've seen this clue in The Globe and Mail.

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