In traffic a repeatedly seen vehicle (3)
I believe the answer is:
car
'vehicle' is the definition.
(car is a kind of vehicle)
'in traffic a repeatedly' is the wordplay.
'in' indicates the answer is hidden within the clue.
'CAR' is hidden within 'traffic a repeatedly'.
'seen' is the link.
(Other definitions for car that I've seen before include "Road vehicle; rail coach" , "Personal vehicle" , "Means of transport" , "Passenger vehicle" , "Private transport" .)