Eye layer containing the iris
I believe the answer is:
uvea
'eye layer containing the iris' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for uvea that I've seen before include "Iris's part" , "Part of the eyeball which houses the iris" , "The pigmented layer of the eye" , "bit of mince pie!" , "part of eye be seen" .)