Contender (10)
I believe the answer is:
challenger
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">contender</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know that contender can be written as challenger)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for challenger that I've seen before include "Competitor" , "One who invites an opponent to a duel" , "professor of literature" , "One contesting a title" , "Contender" .)