Forget about crash? (5,3)
I believe the answer is:
write off
I believe this clue is a double definition.
'forget about' is the first definition.
(to write off is to forget about or dismiss)
'crash?' is the second definition.
(crash resulting in a vehicle being written off)
(Other definitions for write off that I've seen before include "expect nothing to come of it" , "Forget about" , "Dismiss as worthless" , "Post application" , "Ruined car" .)