Old kept in, avoiding cold (4)
I believe the answer is:
aged
'old' is the definition.
(similar in meaning)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(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" .)