Ancient stone implement (7)
I believe the answer is:
neolith
'ancient stone implement' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for neolith that I've seen before include "Prehistoric stone tool - hotline (anag)" , "Ancient stone implement" , "Old stone tool" , "maybe used at Stonehenge?" , "Stone Age artefact" .)