Elderly get enclosed, but not initially (4)
I believe the answer is:
aged
'elderly' is the definition.
(synonyms)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for aged that I've seen before include "Senior" , "Geriatric" , "Matured like wine in wood" , "Ripened, matured" , "Time-worn" .)