Perhaps family seat's hiding ancient baggage (7)
I believe the answer is:
holdall
'baggage' is the definition.
(thesaurus)
'perhaps family seat's hiding ancient' is the wordplay.
I cannot really understand how this works, but
'ancient' could be 'old' (similar in meaning) and 'old' is found in the answer.
The remaining letters 'hall' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for holdall that I've seen before include "Big bag" , "Large strong bag with handles or shoulder strap" , "Capacious bag or basket" , "Item of luggage" , "A large soft travelling bag - stuff everything in" .)