Decorated composer died outside party (7)
I believe the answer is:
adorned
'decorated' is the definition.
('adorn' can be a synonym of 'decorate')
'composer died outside party' is the wordplay.
'composer' becomes 'arne' (I've seen this before**).
'died' becomes 'd'.
'outside' is an insertion indicator.
'party' becomes 'do' (do is a kind of party).
'arne'+'d'='arned'
'arned' going around 'do' is 'ADORNED'.
(Other definitions for adorned that I've seen before include "Put on finery" , "Embellished, decorated" , "Decorated, bedecked" , "Bedecked while Don read" , "done up" .)