Star in Scorpio (7)
I believe the answer is:
'star in scorpio' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for antares that I've seen before include "brilliant point" , "Red supergiant star in Scorpio; nae star (anag.)" , "Star reddened" , "RS [RED STAR]" , "Red supergiant star in Scorpius" .)