Outline in which one car is overturned (8)
I believe the answer is:
scenario
'outline' is the definition.
(I've seen this before)
'one car is overturned' is the wordplay.
'overturned' indicates an anagram.
'one'+'car'+'is'='onecaris'
'onecaris' is an anagram of 'SCENARIO'.
'in which' acts as a link.
(Other definitions for scenario that I've seen before include "plotting for a film" , "Storyline" , "Film treatment" , "Story outline" , "expected sequence of events" .)