Embellish composition of notes (7)
I believe the answer is:
festoon
'embellish' is the definition.
(festooning is a kind of embellishing)
'composition of notes' is the wordplay.
'composition' indicates an anagram.
'of'+'notes'='ofnotes'
'ofnotes' with letters rearranged gives 'FESTOON'.
(Other definitions for festoon that I've seen before include "Decorate with hanging ornaments" , "Hung garland" , "swag" , "Ornamental garland" , "Ornamental chain/garland" .)