Displeasing action against the defence (9)
I believe the answer is:
offensive
'displeasing' is the definition.
(similar in meaning)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for offensive that I've seen before include "Insulting, loathsome" , "Causing resentment or upset" , "nasty in another part of speech" , "Insulting or repulsive" , "Insulting like aggressive attack" .)