Medallion (7)
I believe the answer is:
roundel
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">medallion</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I know this)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for roundel that I've seen before include "Small circular window or design" , "Circle identifying aircraft" , "Refrain" , "Circular marker on aircraft" , "Coloured disc" .)