Argument, quarrel (7)
I believe the answer is:
dispute
<span class="explanation-format__ClueExplanation">I believe this clue is a double definition.<br/ ><br/ >'<span class="explanation-format__original">argument</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >'<span class="explanation-format__original">quarrel</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that quarrel can be written as dispute)</span><br/ ><br/ ></span>
(Other definitions for dispute that I've seen before include "conflict" , "Disagree or challenge" , "Row" , "Altercate" , "Question or deny accuracy or validity" .)