Ancient neck ornament (4)
I believe the answer is:
torc
'ancient neck ornament' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for torc that I've seen before include "ancient necklace" , "One gets into a twist" , "Rigid circular necklace" , "Celtic metal neck-ring" , "Metal neck ornament of ancient Britons" .)