Killing of Asian saints so barbaric (13)
I believe the answer is:
assassination
'killing' is the definition.
(assassination is a kind of killing)
'asian saints so barbaric' is the wordplay.
'barbaric' is an anagram indicator (a rough or barbaric form of the letters).
'asian'+'saints'+'so'='asiansaintsso'
'asiansaintsso' is an anagram of 'ASSASSINATION'.
'of' acts as a link.
(Other definitions for assassination that I've seen before include "Ordered killing" , "Political killing" , "Merciful, lenient" , "(Eg, political) murder" , "execution" .)