Police officer seeing shot in the air near corridor in parliament (8,5)
I believe the answer is:
division lobby
'corridor in parliament' is the definition.
(as in the Houses of Parliament)
'police officer seeing shot in the air near' is the wordplay.
'police officer' becomes 'di' (detective inspector).
'seeing' becomes 'vision'.
'shot in the air' becomes 'lob' (tennis).
'near' becomes 'by' (near means close by).
'di'+'vision'+'lob'+'by'='DIVISION-LOBBY'
(Other definitions for division lobby that I've seen before include "Where MPs vote" , "voting with feet here?" , "Campaign for separation perhaps" .)