Musician changing suit in apartment (8)
I believe the answer is:
flautist
'musician' is the definition.
(flautist is a kind of musician)
'changing suit in apartment' is the wordplay.
'changing' is an anagram indicator.
'in' is an insertion indicator.
'apartment' becomes 'flat' (synonyms).
'suit' is an anagram of 'utis'.
'utis' inserted inside 'flat' is 'FLAUTIST'.
(Other definitions for flautist that I've seen before include "James Galway, for example" , "Musician" , "Studio recording period" , "James Galway, say" , "Player of wind instrument" .)