Colorful membrane (4)
I believe the answer is:
iris
'colorful membrane' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for iris that I've seen before include "Coloured eye part" , "Pupil is at the centre of this" , "may open up in camera" , "Nice flower or eye part" , "Circular coloured membrane in the eye" .)