Killing earl’s thug arranged (9)
I believe the answer is:
slaughter
'killing' is the definition.
(slaughter is a kind of killing)
'earl's thug arranged' is the wordplay.
'arranged' is an anagram indicator.
'earls'+'thug'='earlsthug'
'earlsthug' with letters rearranged gives 'SLAUGHTER'.
(Other definitions for slaughter that I've seen before include "Butcher" , "Wholesale killing" , "Killing (of farm animals)" , "Butchery" , "Kill (animals) for food" .)