Many-headed monster
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">many-headed monster</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for hydra that I've seen before include "Stars" , "Many-headed monster of Greek mythology" , "Small red-berried tree" , "Multi-headed monster killed by Hercules" , "Monster Hercules slew" .)