Mountain road
(Other definitions for trail that I've seen before include "Beaten path; lag" , "Track or mark left by something that has passed" , "Dog - track" , "Beaten path; track" , "Need to catch up with" .)
'mountain road' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for pass that I've seen before include "Give indication of not knowing" , "acceptable exam result" , "At Wembley, no shot" , "approved" , "Narrow route through high mountain, like the Khyber" .)