Second musical instrument cut (5)
I believe the answer is:
shorn
'cut' is the definition.
('shorn' can be a synonym of 'cut')
'second musical instrument' is the wordplay.
'second' becomes 's' (common abbreviation).
'musical instrument' becomes 'horn' (horn is a kind of musical instrument).
's'+'horn'='SHORN'
(Other definitions for shorn that I've seen before include "Having taken coat off" , "set upon by strippers?" , "'The Lord tempers the wind to the ..... lamb'" , "Clipped, fleeced" , "Having had fleece removed" .)