Wanderer takes no notice crossing motorway (5)
I believe the answer is:
nomad
'wanderer' is the definition.
(nomad is a kind of wanderer)
'no notice crossing motorway' is the wordplay.
'notice' becomes 'ad' (both can mean an advertisement).
'crossing' is an insertion indicator.
'motorway' becomes 'm'.
'no'+'ad'='noad'
'noad' placed around 'm' is 'NOMAD'.
'takes' is the link.
(Other definitions for nomad that I've seen before include "one must move on" , "Person always on the move" , "Person of no fixed abode" , "Unsettled character" , "A wandering tribesman" .)