Vestibules (7)
I believe the answer is:
lobbies
'vestibules' is the definition.
('lobby' can be a synonym of 'vestibule')
This is all the clue.
(Other definitions for lobbies that I've seen before include "First planet" , "Entrance halls or ante-rooms" , "Tries to influence minister, say" , "Mounts campaign to influence politicians" , "Large entrances or reception areas" .)