Means of exit (6)
I believe the answer is:
egress
'means of exit' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for egress that I've seen before include "Way out or means of exit" , "At the right moment" , "W ay out" , "The act of going out" , "The act of leaving a building" .)