Sounds like the slave seal is leaking. The push rod should stay dry as far as I know.
You might also want to check that the thrust bearing in your clutch is working - that's the bearing that the push rod pushes on the clutch side. If it's not spinning freely the push rod will spin, create a lot of friction and heat in the slave cylinder and cause the fluid to expand...again, might cause enough pressure to push past the seal.
You can also bleed it, won't hurt to try the quick option first.
Jools
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