They put calves under cover (8)

I believe the answer is:

leggings

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

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

Can you help me to learn more?

(Other definitions for leggings that I've seen before include "Ski-pants without stirrups" , "Garments for lower limbs" , "Close-fitting trousers" .)

I've seen this clue in The Irish News.

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