Saw rise of musical group (5)
I believe the answer is:
nonet
'musical group' is the definition.
(group of nine musicians)
'saw rise' is the wordplay.
'saw' becomes 'tenon' (I've seen this before).
'rise' says the letters should be written backwards.
'tenon' backwards is 'NONET'.
'of' acts as a link.
(Other definitions for nonet that I've seen before include "Piece of music for nine" , "Group of nine musicians" , "Instrumental group of nine players" , "Music for nine instruments or voices" , "Musical group" .)