Senior in large room finds receptacle (7)
I believe the answer is:
holdall
'receptacle' is the definition.
(thesaurus)
'senior in large room' is the wordplay.
'senior' becomes 'old' (associated in meaning).
'in' means one lot of letters goes inside another.
'large room' becomes 'hall' (a hall is a large room).
'old' inserted within 'hall' is 'HOLDALL'.
'finds' is the link.
(Other definitions for holdall that I've seen before include "Handled bag" , "Item of luggage" , "Large strong bag with handles or shoulder strap" , "A large soft travelling bag - stuff everything in" , "Large case, with handles" .)