The musician is good - isn’t a flop (7)
I believe the answer is:
pianist
'the musician' is the definition.
(pianist is a kind of musician)
'good isn't a flop' is the wordplay.
'good' becomes 'pi' (old-fashioned term for pious).
'flop' indicates anagramming the letters (a flop is a mistake or poorly executed action).
'isnt'+'a'='isnta'
'isnta' is an anagram of 'anist'.
'pi'+'anist'='PIANIST'
'is' is the link.
(Other definitions for pianist that I've seen before include "Ashkenazy, say" , "key performer" , "Instrumentalist" , "Musician" , "Keyboard player" .)