She may well be blue (4)
I believe the answer is:
iris
'she' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for iris that I've seen before include "Flower and eye membrane" , "Eye part or attractive flower" , "One controlling pupil' s reactions" , "Eye part or pretty flower" , "Goddess of the rainbow in the eye" .)