Eight-armed mollusc (7)
I believe the answer is:
octopus
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">eight-armed mollusc</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 octopus that I've seen before include "Invertebrate sea creature with three hearts" , "person with widespread influence" , "army swimmer" , "Sea creature - pulpo on a Spanish menu" , "large, influential organization" .)