Eye discharge and redness is a common sign of eye disease.
It can be from many things such as:
Obstruction of tear drainage due to abnormal tear ducts or tear duct openings
Excessive production of tears by the tear glands from irritation or inflammation of the surface structures of the eye, or from pain in or around the eye.
Keratitis (inflammation of the cornea)
Blepharitis (inflammation of eyelids)
Lens luxation (displacement)
Uveitis(inflammation of the iris and blood vessel layers within the eye)
Trauma to the eye from a fight, or foreign object.
These are just some possibilities that can be causing the discharge.
You can wash out the eye with saline solution or warm water. This will not fix the problem but may help with any irritation and discomfort the cat is having from it. Do not give your cat human eye drops like visine.
You need to have a vet look at the cat asap. To determine the root cause and prescribe proper meds and treatments. So many of the above conditions I mentioned can cause permanent damage and blindness if not taken care of properly and quickly.
I know you were looking for a home treatment to fix this, but there really isn't one.
Best Wishes, Micki