Clutch reservoir is leaking out of the top when the clutch is depressed. Cap checked and appeares tight, but fluid leaks out of cap area and can't get it into gear. Any ideas on what could cause this?

 

Air in the line? Debris in master cylindar preventing the piston from returning to its normal position?
I have a bad feeling about this one so I don't want to bum steer you so heres a little reading you might like to do: Go to this site Wrangler YJ Forum ('87-'95) [Archive] - JeepsUnlimited.com Forums
Item number 2: '90 YJ leaking brake fluid from clutch housing?
Click on that and then read what these people have said about the possible problem.
I am hoping someone else comes in here and replies to this post with better knews.