I have seen some people use a long breaker bar against the shop floor,
and ease out the clutch, but I don't recommend this unless you know how to keep the socket from popping off the nut.
I have seen people use a huge pipe wrench in the same manner......
Sometimes it can be jolted loose, when steady pressure won't do it.
I have seen people kick the breaker bar with the car jacked up and the brakes on.
I have an impact wrench if you want to bring it over to break it loose.-Bob 839-4281