Entrance hall (5)
(Other definitions for lobby that I've seen before include "Small hall" , "Entrance room" , "Group seeking influence" , "invoking name of pressure group" , "Entrance hall - seek to influence" .)
'entrance hall' is the definition.
(I know that entrance hall can be written as foyer)
This is all the clue.
(Other definitions for foyer that I've seen before include "Reception room or waiting area" , "Hotel entrance hall" , "Theatre public area" , "Theatre entrance hall" , "Vestibule" .)