Goes by the mountain roads (6)
I believe the answer is:
passes
'goes by' is the definition.
('pass' can be a synonym of 'go by')
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for passes that I've seen before include "never fails to get?" , "'Men seldom make . . . at girls who wear glasses'" , "Written permissions for absences" , "goes beyond" , "Tickets" .)