Shutter of Leica only opening to one diameter? Yes, as reported initially (6)
I believe the answer is:
eyelid
'shutter' is the definition.
(I have seen 'Facial shutter' mean 'eyelid' so perhaps 'shutter' could also mean 'eyelid')
'diameter? yes as reported initially' is the wordplay.
'diameter?' becomes 'lid' (I can't explain this - if you can you should believe this answer much more).
'yes' becomes 'aye' ('aye' means 'yes').
'as reported' shows a homophone (sound like).
'initially' says to put letters next to each other (some letters go before others).
'aye' is a homophone of 'eye'.
'lid' after 'eye' is 'EYELID'.
'of leica only opening to one' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for eyelid that I've seen before include "Optical membrane" , "Natural optic protector" , "Fold of skin on the face" , "Covering for organ of sight" , "Protective cover" .)