Specters (6)
I believe the answer is:
ghosts
'specters' is the definition.
('ghost' can be a synonym of 'specter')
This is the entire clue.
(Other definitions for ghosts that I've seen before include "Spirits or apparitions" , "Apparitions of a dead people" , "Spooks, spectres" , "Writes for another; Ibsen play" , "Spectres, wraiths" .)