Summary of plot involving one car is altered (8)
I believe the answer is:
scenario
'summary of plot' is the definition.
(I've seen this before)
'one car is altered' is the wordplay.
'altered' is an anagram indicator.
'one'+'car'+'is'='onecaris'
'onecaris' is an anagram of 'SCENARIO'.
'involving' acts as a link.
(Other definitions for scenario that I've seen before include "Outline -- setting for a novel" , "Outline or synopsis of a play" , "expected sequence of events" , "plotting for a film" , "Outlines of drama" .)