Iris may be behind it (6)
I believe the answer is:
eyelid
'iris' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for eyelid that I've seen before include "It blinks" , "Facial shutter" , "Batting membrane?" , "Skin over viewer" , "Ocular closer" .)