Answer:
A word I know, six letters it contains. Subtract just one and twelve remains.
Late afternoons I often bathe. I'll soak in water piping hot. My essence goes through. My see through clothes. Used up am I - I've gone to pot.
What comes once in a minute, twice in a moment, but never in a thousand years?
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.
I am the greatest teacher out of them all, but alas in the end I kill my pupils.
Often cooked as fillet, this meat comes from an animal that swims underwater.