Heavenly body of retrospective designer - and French sex appeal (8)
I believe the answer is:
asteroid
'heavenly body' is the definition.
(asteroid is a kind of heavenly body)
'retrospective designer and french sex appeal' is the wordplay.
'retrospective' is a reversal indicator.
'designer' becomes 'dior' (dior is a designer brand).
'and french' becomes 'et' ('and' in the French language).
'sex appeal' becomes 'sa'.
'dior'+'et'+'sa'='dioretsa'
'dioretsa' backwards is 'ASTEROID'.
'of' is the link.
(Other definitions for asteroid that I've seen before include "Small heavenly body" , "Any of the small planets revolving around the sun" , "Small rock orbiting the sun" , "Small rocky object orbiting the sun - store aid (anag)" , "space traveller" .)