Top-grade drug shaped like a star (8)
I believe the answer is:
asteroid
'shaped like a star' is the definition.
I can't judge whether this defines the answer.
'top-grade drug' is the wordplay.
'top grade' becomes 'A' (top academic grade).
'drug' becomes 'steroid' (type of drug).
'a'+'steroid'='ASTEROID'
Can you help me to learn more?
(Other definitions for asteroid that I've seen before include "space traveller" , "Small planet revolving round the sun" , "Small heavenly body" , "Any of the small planets revolving around the sun" , "Rocky body in orbit" .)