Motorway, eg (4)
I believe the answer is:
road
'motorway eg' is the definition.
(motorway is a kind of road)
This is all the clue.
(Other definitions for road that I've seen before include "course" , "'The . . . . to hell is paved with good intentions'" , "Parting guests used to take 'one for the --'" , "Highway or byway" , "Route travelled by sea" .)