Arguer (7)
I believe the answer is:
debater
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">arguer</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for debater that I've seen before include "speaker at Oxford Union" , "One discussing topic" , "One engaged in public argument" , "One in formal discussion" , "argumentative person" .)