Reportedly understands harmony being part of spectacles (9)
I believe the answer is:
nosepiece
'part of spectacles' is the definition.
('nosepiece' is part of 'spectacles')
'reportedly understands harmony' is the wordplay.
'reportedly' indicates a 'sounds like' (homophone) clue.
'understands' becomes 'knows' (understand can mean to know or recognise).
'harmony' becomes 'piece' (I am not sure about this - if you are sure you should believe this answer much more).
'knows' is a homophone of 'nose'.
'nose'+'piece'='NOSEPIECE'
'being' is the link.
Can you help me to learn more?
(Other definitions for nosepiece that I've seen before include "Protector" , "some armour" , "bridge" , "Guard at front" , "bit of protection" .)