Affair of timeless caste (4)
I believe the answer is:
case
'affair' is the definition.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for case that I've seen before include "A proceeding in a court of law" , "Piece of luggage and a lawyer's proceeding" , "Container and court proceeding" , "Legal action; container" , "A law suit or a container" .)