Fibrous constituent of feathers, hair, horns, etc (7)

I believe the answer is:

keratin

(Other definitions for keratin that I've seen before include "Material in hooves and nails" , "Hair, nails substance" , "Constituent of hair/nails" , "Rate ink (anag) - fibrous protein" , "Protein found in hair and nails" .)

I've seen this clue in the Sydney Morning Herald.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.