This could be from air in the system.
I would reconnect the line to the slave and bleed air from that valve.
This is from Desert's DIY writeup on bleeding brake lines. It is basically the same procedure for the clutch master cylinder.
have an assistant pump the brake pedal slowly and evenly several times,,ask them to hold the pedal down, ,
loosen up the bleeder screw to let the air in the system escape, it is a good idea to put a hose from the bleeder screw going into a container , that way you do not splash brake fluid all over ,, while pedal is still down retighten the bleeder screw,, repeat it, till no more air comes out..
Remember not to let the reservoir go empty,, so it is a good idea to check and fill it after each wheel has been bled,,
2005 Acura TSX MT