Flush, flush, and flush again! That could happen if the mechanic didn’t thoroughly bleed the system after your clutch work. I recommend doing the gravity bleed as suggested earlier. That way you’ll be able to see if and when the li es are clear and clean fluid is coming out. It’s really easy to do. The biggest job you’ll have is keeping the master cylinder full of fluid by constantly topping it off. You don’t want it to run dry, or you’ll introduce more air into the system and it will take longer to bleed. You can even drink a beer, or two, or three during the process.