A viewer's girl? (4)
I believe the answer is:
iris
This might be a double definition.
'a viewer's' is the first definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe there's an association between them I don't understand?
'girl?' is the second definition.
(girl's name)
Can you help me to learn more?
(Other definitions for iris that I've seen before include "Flag - part of eye" , "Flag or flower in the eye" , "Plant - part of the eye" , "--- Murdoch, author" , "may open up in camera" .)