Heavenly body of a bodybuilder? (8)
I believe the answer is:
asteroid
'heavenly body' is the definition.
(asteroid is a kind of heavenly body)
'a bodybuilder?' is the wordplay.
'bodybuilder?' becomes 'steroid' (as in the type of drug).
'a'+'steroid'='ASTEROID'
'of' is the link.
(Other definitions for asteroid that I've seen before include "looking like a star?" , "Bit of rock that moves around the heavens" , "space traveller" , "Small heavenly body" , "Small rocky object orbiting the sun - store aid (anag)" .)