Prehistoric object (6)
I believe the answer is:
fossil
<span class="explanation-format__ClueExplanation">I believe this is a double definition.<br/ ><br/ >'<span class="explanation-format__original">prehistoric</span>' is the first definition.<br/ ><span class="explanation-format__explanation">(thesaurus)</span><br/ ><br/ >'<span class="explanation-format__original">object</span>' is the second definition.<br/ ><span class="explanation-format__explanation">(I know that fossil is a type of object)</span><br/ ><br/ ></span>
(Other definitions for fossil that I've seen before include "Petrified 9" , "The remains of a plant or animal that existed in a past geological age" , "Antiquated person" , "Prehistoric relic" , "Remnant of life in a rock" .)