Your looking at one of several things:
- Bad Master Cylinder
- Bad Slave cylinder
- Broken fluid line
- Broken clutch pressure plate (unlikely)
Usually you'd replace the master and slave cylinders as a set. But on the 87 and 88 cherokees (and most likely comanches) with the Pugeot transmission, the slave cylinder and throwout bearing are one piece and must be replaced as a unit as well (which requires dropping the Transmission)
-Nick