Answer:

keratin

Answer	Crossword Clue
KERATIN	Horn material
KERATIN	Tissues of fingernails.
KERATIN	Basis of horny tissue.

KERATIN	Fingernail component.
KERATIN	Nail or horn base
KERATIN	Fibrous protein
KERATIN	A fibrous protein
KERATIN	Protein in hair and nails
KERATIN	Hair protein
KERATIN	Fingernail makeup
KERATIN	Nail material

KERATIN	Fingernails, essentially
KERATIN	Protein found in hair and hooves