Poisonous arachnid (8)
I believe the answer is:
scorpion
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">poisonous arachnid</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 scorpion that I've seen before include "Small spider with pincers and stinging tail" , "Arachnid with venomous sting" , "Eight sign of Zodiac, kind of spider" , "Poisonous arachnid" , "Stinging creature" .)