Scores piece, finale from Debussy (4)
I believe the answer is:
many
'scores' is the definition.
(thesaurus)
'piece finale from debussy' is the wordplay.
'piece' becomes 'man' (synonyms).
'finale from' says to take the final letters.
The last letter of 'debussy' is 'y'.
'man'+'y'='MANY'
(Other definitions for many that I've seen before include "Several" , "A great number" , "regarded as a large number" , "Numerous" , "Multitudinous" .)