Roadside in stockbroker belt (4)
I believe the answer is:
kerb
'roadside' is the definition.
(I've seen this before)
'in stockbroker belt' is the wordplay.
'in' indicates the answer is hidden within the clue.
'KERB' is hidden within 'stockbroker belt'.
(Other definitions for kerb that I've seen before include "Edge of road" , "Roadway edge" , "on the borderline?" , "Stone edging to footpath" , "Pavement's edge" .)