US bass-baritone has abandoned nudism? (7)

I believe the answer is:

robeson

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

I can't explain the rest of the clue.

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(Other definitions for robeson that I've seen before include "Paul -. US bass singer and actor" , "Paul ......., great American bass singer and actor (" .)

I've seen this clue in The Independent.

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