Part of a building for accommodating the old (5)
I believe the answer is:
foyer
'part of a building' is the definition.
('foyer' is part of 'building')
'for accommodating the old' is the wordplay.
'accommodating' is an insertion indicator.
'the old' becomes 'ye'.
'for' enclosing 'ye' is 'FOYER'.
(Other definitions for foyer that I've seen before include "Reception lobby" , "Reception room or waiting area" , "Large entrance area" , "Theatrical" , "Theatre public area" .)