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 quite see how this works, but
'ancient' could be 'old' (similar in meaning) and 'old' is found within the answer.
The remaining letters 'hall' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
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" .)