Action English novelist mentioned (3)
I believe the answer is:
war
'action' is the definition.
(war is a kind of action)
'english novelist mentioned' is the wordplay.
'english novelist' becomes 'waugh' (novelist Evelyn Waugh).
'mentioned' shows a homophone (sound like).
'waugh' is a homophone of 'WAR'.
(Other definitions for war that I've seen before include "Battle" , "Fight" , "Combat" , "Open hostility" , "State of armed conflict" .)