Looker-on (9)
I believe the answer is:
spectator
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">looker-on</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for spectator that I've seen before include "He attends matches" , "Cat poster (anag.)" , "one found at ground?" , "observer" , "Onlooker; magazine" .)