Flag lady (4)
I believe the answer is:
I believe this is a double definition.
'flag' is the first definition.
(type of iris flower)
'lady' is the second definition.
(Other definitions for iris that I've seen before include "Pupil's place?" , "Pupil is at the centre of this" , "Plant - part of the eye" , "Flag - surrounding pupil" , "Flag,flower and part of the eye" .)