Player of instrument shows excessive desire to hold note (6)
I believe the answer is:
lutist
'player of instrument' is the definition.
(someone playing a lute)
'excessive desire to hold note' is the wordplay.
'excessive desire' becomes 'lust' (lust can mean excessive or unhealthy desire).
'to hold' means one lot of letters goes inside another.
'note' becomes 'ti' (musical note as in do re mi so fa la ti).
'lust' going around 'ti' is 'LUTIST'.
'shows' acts as a link.
(Other definitions for lutist that I've seen before include "string player" , "musician" .)