A claw was a relatively long, sharp piece of keratin at the end of an animal's feet or paws, similar to nails. Species with claws generally used them to either kill prey, hold onto things, attack, or a combination thereof. Attacking with claws was called scratching or clawing.
When William T. Riker was trying to feed Spot, she scratched him, and he got treated by Beverly Crusher. (TNG: "Timescape")
On the planet of the Sky Spirits, Neelix was attacked by a hawk that clawed him just above his right eye. (VOY: "Tattoo")