Organ used by Meyerbeer (3)
I believe the answer is:
eye
'organ' is the definition.
(eye is a kind of organ)
'used by meyerbeer' is the wordplay.
'used by' indicates the answer is hidden within the clue.
'EYE' is hidden within 'meyerbeer'.
(Other definitions for eye that I've seen before include "Organ of sight" , "Look at, scrutinise" , "Orb" , "Oculus" , "Glance" .)