Joe hiding artist's sign (6)
I believe the answer is:
gemini
'sign' is the definition.
(Gemini is a star sign)
'joe hiding artist's' is the wordplay.
'joe' becomes 'GI' (GI Joe).
'hiding' indicates putting letters inside.
'artist' becomes 'emin' (Tracey Emin).
'gi' going around 'emin' is 'GEMINI'.
(Other definitions for gemini that I've seen before include "Zodiac sign - the Twins" , "Twins star-sign" , "star group" , "Zodiacal twins" , "Twins star sign" .)