Musician's desire to hold note (6)
I believe the answer is:
lutist
'musician's' is the definition.
(I've seen this before)
'desire to hold note' is the wordplay.
'desire' becomes 'lust' (lusting is a kind of desiring).
'to hold' indicates putting letters inside.
'note' becomes 'ti' (musical note, as in do re mi so fa la ti do).
'lust' placed around 'ti' is 'LUTIST'.
(Other definitions for lutist that I've seen before include "musician" , "string player" .)