Mythical winged horse (7)
I believe the answer is:
pegasus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">mythical winged horse</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 pegasus that I've seen before include "fabulous horse" , "Mount flying" , "Winged horse - constellation" , "Immortal winged horse of Greek mythology" , "high horse" .)