Film outline in which arsenic wrecked love (8)
I believe the answer is:
scenario
'film outline' is the definition.
'arsenic wrecked love' is the wordplay.
'wrecked' is an anagram indicator.
'love' becomes 'o' (In tennis, 'love' means 'zero').
'arsenic' with letters rearranged gives 'scenari'.
'scenari'+'o'='SCENARIO'
'in which' is the link.
(Other definitions for scenario that I've seen before include "Outline of dramatic work" , "expected sequence of events" , "Film/novel plot outline" , "Production plan" , "Written outline of a film, novel, or stage work" .)