Musical group or artist's carrying case (9)
I believe the answer is:
orchestra
'musical group' is the definition.
(orchestra is a kind of musical group)
'or artist's carrying case' is the wordplay.
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'carrying' means one lot of letters go next to another.
'case' becomes 'chest' ().
'ra' after 'chest' is 'chestra'.
'or'+'chestra'='ORCHESTRA'
(Other definitions for orchestra that I've seen before include "Noted performers" , "Eg, LSO, RPO" , "kitchen setting?" , "Large group of players" , "eg Halle" .)