Piece of rock that moves around the heavens (8)
I believe the answer is:
asteroid
'piece of rock that moves around the heavens' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for asteroid that I've seen before include "Minor planet" , "Piece of rock that moves around the heavens" , "Small celestial body composed of rock and metal" , "Small celestial body moving around the sun" , "Bits of rock that move around the heavens" .)