Flag girl, a bit of an eyeful (4)

I believe the answer is:

iris

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'flag' is the definition.
(type of iris flower)

I cannot understand how the remainder of the clue works.

(Other definitions for iris that I've seen before include "Woman" , "Rainbow-goddess" , "A flower; spirit conjured in Tempest" , "Plant with sword-shaped leaves" , "Flowers in the eye?" .)

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