Heartlessly carries on wrecking screenplay (8)
I believe the answer is:
scenario
'screenplay' is the definition.
(I've seen this in another clue)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for scenario that I've seen before include "Outline -- setting for a novel" , "Dramatic set-up" , "Event postulation" , "Film treatment" , "Written outline of a film or play" .)