Clutch slave or master cylinder. It could have air in the system but I believe you said it was leaking. If you replace the slave and master cylinder be sure to check your line that goes between them. Some are metal some are rubber. If it is rubber replace it too but replace it back with rubber because sometimes you get in a deal with the ends mathing up on the metal and rubber lines. It going to take you about a two bottles of brake fluide to bleed the air out. That's the small bottles but I buy the big bottles because I have a lot of things to keep up. Just when you think you have all the air out drive it a day or two and if it starts grinding some bleed it again and that should have it.