Minor planet yields a compound (7)
I believe the answer is:
steroid
'compound' is the definition.
(steroid is a kind of compound)
'minor planet yields a' is the wordplay.
'minor planet' becomes 'asteroid' (synonyms).
'yields' indicates named letters should be taken away.
'asteroid' with 'a' taken away is 'STEROID'.
(Other definitions for steroid that I've seen before include "Organic compound" , "growth medication" , "Performance-enhancer illegal for athletes" , "Compound used as drug or performance enhancer" , "Type of drug, maybe anabolic" .)