Entrance where those not invited can crash? (4)
I believe the answer is:
gate
I believe this is a double definition.
'entrance' is the first definition.
(type of entrance)
'where those not invited can crash?' is the second definition.
(as in gatecrashing)
(Other definitions for gate that I've seen before include "Attendance figure" , "Number of people admitted to a sporting event" , "Entry to arena" , "Plane-boarding point" , "Narrow opening" .)