Don't accept what has already been rejected (6)

I believe the answer is:

refuse

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'don't' is the definition.
Both the definition and answer are singular nouns.
Perhaps there's a link between them I don't understand?

I cannot understand how the remainder of the clue works.

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(Other definitions for refuse that I've seen before include "Turn away" , "Say no to - rubbish" , "Say no to garbage" , "litter" , "Decline, repudiate" .)

I've seen this clue in The Irish Independent.

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