Measure round a highway (4)
I believe the answer is:
road
'highway' is the definition.
(thesaurus)
'measure round a' is the wordplay.
'measure' becomes 'rod' (rod is a kind of measure**).
'round' is an insertion indicator.
'rod' going around 'a' is 'ROAD'.
(Other definitions for road that I've seen before include "Mine passage; way" , "Abbey -, Beatles album" , "See 10" , "motorway?" , "'The . . . . to hell is paved with good intentions'" .)