Mythical fire-breather (6)
I believe the answer is:
dragon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mythical fire-breather</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 dragon that I've seen before include "Virago" , "Flying monster of Welsh legend" , "[TERMAGANT]" , "Continue interminably" , "Fire-breathing beast" .)