Passenger just picked up (4)
I believe the answer is:
fare
'passenger' is the definition.
(fare is a kind of passenger)
'just picked up' is the wordplay.
'just' becomes 'fair' ('fair' is associated in meaning with 'just').
'picked up' shows a homophone (sound like).
'fair' is a homophone of 'FARE'.
(Other definitions for fare that I've seen before include "Food - money for travelling - get on" , "Food, or price of bus ticket" , "Price of passage" , "Grip (of a tyre)" , "Payment for journey" .)