its most likely your clutch master cylinder.  don't bother bench bleeding
it, its not necessary.  clamp the feed hose, open the slave bleeder and
drain the system.  change the cylinder, unclamp the feed hose and pump the
pedal a couple of times with a length of hose attached to the slave
bleeder and emptying into a container.  pump the peddle until there is
good flow through the system.  i recommend pumping at least a small
bottle of brake fluid threw the system to clean the metal particles out of
the slave or you will be replacing the slave in short order also.  then
bleed the system as normal.

jonathan