Eight-sided figure (7)
I believe the answer is:
octagon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">eight-sided figure</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 octagon that I've seen before include "Eight-sided object" , "regular form" , "Figure with 8 sides" , "plane figure" , "Eight sided figure" .)