Sign of the twins (6)
I believe the answer is:
gemini
'sign of the twins' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for gemini that I've seen before include "Zodiacal twins" , "Sign of the Twins ( 6)" , "lot of stars" , "set of twinklers" , "Zodiac sign - the Twins" .)