Any congenital growth or pigmented blemish on the skin (6)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
naevus
(Other definitions for naevus that I've seen before include "A scarlet birthmark on skin" , "A red birthmark on skin" , "Birthmark or mole" , "Spot" , "disfiguring mark" .)