Found in large room, ancient bag (7)
I believe the answer is:
holdall
'bag' is the definition.
(holdall is a kind of bag)
'found in large room ancient' is the wordplay.
'found in' indicates putting letters inside.
'large room' becomes 'hall' (I've seen this before).
'ancient' becomes 'old' ('old' can be similar in meaning to 'ancient').
'hall' placed around 'old' is 'HOLDALL'.
(Other definitions for holdall that I've seen before include "Item of luggage" , "Large strong bag with handles or shoulder strap" , "A large soft travelling bag - stuff everything in" , "Big bag" , "Large bag (no need for another?)" .)