Instrument of empty honour (4)
I believe the answer is:
oboe
'instrument' is the definition.
(type of musical instrument)
'empty honour' is the wordplay.
'empty' becomes 'o'.
'honour' becomes 'boe' (I can't justify this - if you can you should believe this answer much more).
'o'+'boe'='OBOE'
'of' is the link.
(Other definitions for oboe that I've seen before include "Walk with exaggerated movements" , "music producer" , "Slender double-reed instrument" , "Woodwind instrument of treble pitch" , "Double-reeded woodwind instrument" .)