Flower; part of the eye (4)
I believe the answer is:
iris
I believe this clue is a triple definition!
'flower' is the first definition.
(I've seen this before)
'part' is the second definition.
(iris is a kind of part)
'of' acts as a link.
'the eye' is the third definition.
(thesaurus)
(Other definitions for iris that I've seen before include "Rainbow - flag" , "Eye part or pretty flower" , "Flag - part of eye" , "plant with showy flowers" , "Garden flower - part of eye" .)