Throw up next to hall (5)
I believe the answer is:
lobby
'hall' is the definition.
('lobby' can be a synonym of 'hall')
'throw up next to' is the wordplay.
'throw up' becomes 'lob' (I've seen this before).
'next to' becomes 'by'.
'lob'+'by'='LOBBY'
(Other definitions for lobby that I've seen before include "Shy" , "invoking name of pressure group" , "Small hall" , "Antechamber" , "Hallway; seek to influence" .)