Vehicle in traffic, initially following another (4)
I believe the answer is:
cart
'vehicle' is the definition.
(I know that cart is a type of land vehicle)
'traffic initially following another' is the wordplay.
'initially' says to take the initial letters.
'following' means one lot of letters go next to another.
'another' becomes 'car' (I've seen this in other clues).
The initial letter of 'traffic' is 't'.
't' after 'car' is 'CART'.
'in' acts as a link.
(Other definitions for cart that I've seen before include "Carrying vehicle" , "Horse-drawn vehicle" , "Pulled vehicle" , "Open vehicle" , "Don't put this before the horse (4)" .)