Signs up? (6)
I believe the answer is:
zodiac
'signs up?' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for zodiac that I've seen before include "nd of sky divided into twelve parts" , "Heavenly belt of star-signs" , "Imaginary belt in the heavens" , "Astrologers' set of signs" , "Star sign chart" .)