Musician changing suit in apartment (8)
I believe the answer is:
flautist
'musician' is the definition.
(I know that flautist is a type of musician)
'changing suit in apartment' is the wordplay.
'changing' indicates anagramming the letters.
'in' indicates putting letters inside.
'apartment' becomes 'flat' (synonyms).
'suit' is an anagram of 'utis'.
'utis' placed within '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" .)