Pupil surrounder (4)
I believe the answer is:
iris
'pupil surrounder' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for iris that I've seen before include "Fleur-de-lis" , "Garden flower - part of eye" , "Flag,flower and part of the eye" , "Female" , "Flag - flower - girl" .)