Giant with a hundred eyes (5)
I believe the answer is:
argus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">giant with a hundred eyes</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 argus that I've seen before include "Legendary Guardian" , "Monster with many eyes slain by Hermes in Greek myth" , "Giant with one hundred eyes in Greek mythology" , "Alert watchman" , "Various brown butterflies" .)