Paints loudly, scores badly (7)
I believe the answer is:
frescos
'paints' is the definition.
(frescoing is a kind of painting)
'loudly scores badly' is the wordplay.
'loudly' becomes 'f' (short for forte - 'loud' in music).
'badly' is an anagram indicator (letters in the wrong order).
'scores' anagrammed gives 'rescos'.
'f'+'rescos'='FRESCOS'
(Other definitions for frescos that I've seen before include "Murals done on wet plaster" , "Art" .)