They dont get worn out (7)

I believe the answer is:

pyjamas

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'out' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for pyjamas that I've seen before include "Bed clothes" , "Night attire" , "Sleeping attire" , "Bedclothes" , "Pays Maj poorly to wear them" .)

I've seen this clue in The Irish Independent.

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