Crossword Genius

Old kept in, avoiding cold (4)

Ross

I believe the answer is:

aged

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'old' is the definition.
(similar in meaning)

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

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(Other definitions for aged that I've seen before include "Long in the tooth" , "Like Uncle Arly" , "Getting on" , "Very old, person or wine" , "Ripened, matured" .)

I've seen this clue in The Times.
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