Disheartened fighter rejected harsh conflict (4,3)
I believe the answer is:
boer war
'conflict' is the definition.
(I've seen this before)
'disheartened fighter rejected harsh' is the wordplay.
'disheartened' means to remove the middle letters.
'fighter' becomes 'boxer' (boxer is a kind of fighter).
'rejected' says the letters should be written backwards.
'harsh' becomes 'raw' (I am not sure about this - if you are sure you should believe this answer much more).
'boxer' with its centre taken out is 'boer'.
'raw' backwards is 'war'.
'boer'+'war'='BOER WAR'
Can you help me to learn more?
(Other definitions for boer war that I've seen before include "historic set-to" , "'One of two armed conflicts in southern Africa (4,3)'" , "Armed conflict between Britain and S Africa a century ago" , "Conflict in southern Africa" , "Either of two conflicts fought by Britain in S Africa" .)