Prehistoric object (6)
I believe the answer is:
fossil
I believe this is a double definition.
'prehistoric' is the first definition.
(thesaurus)
'object' is the second definition.
(I know that fossil is a type of object)
(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" .)