Highway travelled by horse noisily (4)
I believe the answer is:
road
'highway' is the definition.
(highway is a type of road)
'travelled by horse noisily' is the wordplay.
'travelled by horse' becomes 'rode'.
'noisily' indicates a 'sounds like' (homophone) clue.
'rode' is a homophone of 'ROAD'.
(Other definitions for road that I've seen before include "Street" , "See 10" , "motorway?" , "See 2" , "Abbey -, Beatles album" .)