Artificial organ composer Tees heard (5,3)
I believe the answer is:
glass eye
'artificial organ' is the definition.
(I've seen this before)
'composer tees heard' is the wordplay.
'composer' becomes 'glass' (I can't explain this - if you can you should give a lot more credence to this answer).
'tees' becomes 'I' (where the crossword setter is 'Tees').
'heard' shows a homophone (sound like).
'i' is a homophone of 'eye'.
'glass'+'eye'='GLASS EYE'
Can you help me to learn more?
(Other definitions for glass eye that I've seen before include "no real looker?" , "Ocular prosthetic" , "Artificial organ" , "False socket filler" , "Optical replacement" .)