Aggressive driver (7)
(Another definition for roadhog that I've seen is " Reckless driver".)
'aggressive driver' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for road hog that I've seen before include "Driving pig?" , "Boorish driver" , "menace behind the wheel" , "Boorishly reckless driver" , "Bad driver" .)