With a gun, covering the access route (4)
I believe the answer is:
road
'route' is the definition.
(I know that route can be written as road)
'with a gun' is the wordplay.
'with' indicates putting letters inside.
'gun' becomes 'rod' (rod is a kind of gun).
'a' going within 'rod' is 'ROAD'.
'covering the access' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for road that I've seen before include "motorway?" , "Parting guests used to take 'one for the --'" , "Street" , "Abbey -, Beatles album" , "Path" .)