Musicians turning to entertaining and so on (5)
I believe the answer is:
octet
'musicians' is the definition.
(I've seen this before)
'turning to entertaining and so on' is the wordplay.
'turning' shows that the letters should be reversed in order.
'entertaining' means one lot of letters goes inside another (inviting in, as for dinner).
'and so on' becomes 'etc' (synonyms).
'to' enclosing 'etc' is 'tetco'.
'tetco' written backwards gives 'OCTET'.
(Other definitions for octet that I've seen before include "Piece for eight players" , "Lines of verse" , "Group that plays" , "Eight people together" , "Mendelssohn or Schubert piece" .)