Warlike officer, we hear (7)
I believe the answer is:
martial
'warlike' is the definition.
('martial' can be a synonym of 'warlike')
'officer we hear' is the wordplay.
'officer' becomes 'marshal' (I've seen this before).
'we hear' shows a homophone (sound like).
'marshal' is a homophone of 'MARTIAL'.
(Other definitions for martial that I've seen before include "These arts concern fighting sports" , "Relating to hostilities" , "poet of ancient times" , "Warlike; Roman poet" , "Relating to the armed forces" .)