Plot involved car noise (8)
I believe the answer is:
scenario
'plot' is the definition.
(thesaurus)
'involved car noise' is the wordplay.
'involved' is an anagram indicator (involved can mean confusing or complex).
'car'+'noise'='carnoise'
'carnoise' with letters rearranged gives 'SCENARIO'.
(Other definitions for scenario that I've seen before include "In plot of movie, for instance" , "Imagined situation" , "Iron case (anag)" , "plotting for a film" , "Written outline of a film or play" .)