Be a passenger in a car, ideally (4)
I believe the answer is:
ride
'be a passenger' is the definition.
(I've seen this in another clue)
'in a car ideally' is the wordplay.
'in' says the answer is hidden in the clue.
'RIDE' can be found hidden inside 'car ideally'.
(Other definitions for ride that I've seen before include "Sit on (a horse/vehicle)" , "Journey on horse?" , "spin > lift > pedal" , "Travel in or be carried on" , "Go by bicycle" .)