Part number one? I'll never Tell,
but when you figure it out, drop the last L
Part two is straightforward, though a little crass:
give the plural form of what comes out your ...
The third and final part, you'll see
can be found by thinking empirically
What word am I describing?
Edit -- no guesses after 20 hours, so here's a hint:
I said I'll never Tell, though I'll gladly open a few more Gates