Disgusting campaign of aggression (9)
I believe the answer is:
offensive
I believe this clue is a triple definition!
'disgusting' is the first definition.
(similar in meaning)
'campaign' is the second definition.
(I have seen 'Aggressive campaign' mean 'offensive' so perhaps 'campaign' could also mean 'offensive')
'of' acts as a link.
'aggression' is the third definition.
(thesaurus)
(Other definitions for offensive that I've seen before include "Insulting like aggressive attack" , "Causing resentment or upset" , "Insulting, disgusting" , "Insulting, loathsome" , "drive" .)