A fight in the car ahead (7)
I believe the answer is:
forward
'ahead' is the definition.
(I know that ahead can be written as forward)
'a fight in the car' is the wordplay.
'a fight' becomes 'war' (I've seen this in another clue).
'in the' is an insertion indicator.
'car' becomes 'ford' (Ford is a make of car).
'war' put into 'ford' is 'FORWARD'.
(Other definitions for forward that I've seen before include "Bold, overfamiliar" , "Onward" , "26 [RUGBY] player" , "Send on; football player" , "Ahead; impertinent" .)