Using drone in conflict is decisive (10)
I believe the answer is:
resounding
'decisive' is the definition.
(I've seen this before)
'using drone in conflict' is the wordplay.
'in conflict' is an anagram indicator (letters clashing or in conflict with each other).
'using'+'drone'='usingdrone'
'usingdrone' is an anagram of 'RESOUNDING'.
'is' is the link.
(Other definitions for resounding that I've seen before include "Booming" , "Decisive" .)