Iris ring (6)
I believe the answer is:
areola
'iris ring' 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 "Circular coloured area, especially around nipple" , "Pigmented area around a nipple" , "Ring" , "Slightly sunken spot" , "special type of circle" .)