Major conflict (3)
I believe the answer is:
war
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">major conflict</span>' is the definition.<br/ ><span class="explanation-format__explanation">(a war is a major outbreak of fighting)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for war that I've seen before include "Large-scale conflict" , "Combat" , "State of armed struggle" , "Armed hostility" , "Fight" .)