Hawker, one using a bike, we hear (6)
I believe the answer is:
pedlar
'hawker' is the definition.
(both can mean somebody selling something)
'one using a bike we hear' is the wordplay.
'one using a bike' becomes 'peddler' (someone peddling a bike).
'we hear' indicates a 'sounds like' (homophone) clue.
'peddler' sounds like 'PEDLAR'.
(Other definitions for pedlar that I've seen before include "Itinerant vendor" , "Travelling seller" , "Itinerant salesman" , "Itinerant seller" , "Itinerant trader" .)