Heard officer fighting (7)
I believe the answer is:
martial
'fighting' is the definition.
(thesaurus)
'heard officer' is the wordplay.
'heard' shows a homophone (sound like).
'officer' becomes 'marshal' (I've seen this before).
'marshal' is a homophone of 'MARTIAL'.
(Other definitions for martial that I've seen before include "Relating to the military" , "Warlike; Roman poet" , "Of war or the armed forces" , "Belligerent" , "Soldierly (arts?)" .)