Iris feature (6)
I believe the answer is:
areola
'iris feature' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for areola that I've seen before include "Pigmented area around a nipple" , "Slightly sunken spot" , "Ring" , "special type of circle" , "Circular coloured area, especially around nipple" .)