Fire-breathing monster (6)
I believe the answer is:
dragon
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">fire-breathing monster</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for dragon that I've seen before include "Formidable woman" , "Fiery reptile or person" , "Legendary fire-breather" , "Mythological fire-breathing creature" , "Fire-breathing reptile, usually with wings" .)