Ear, say, for a musical instrument (5)
I believe the answer is:
organ
I believe this is a double definition.
'ear say' is the first definition.
(ear is a kind of organ)
'a musical instrument' is the second definition.
(organ is a kind of musical instrument)
'for' acts as a link.
(Other definitions for organ that I've seen before include "Wind and keyboard instrument" , "with a lofty tone?" , "Eg, heart/liver" , "music producer" , "notes issue from this" .)