I've got a friend. You haven't met him yet, so I'll tell you about him.
Hey, are you listening? I'll quiz you! Sound fair?
This guy, he's a bit of a trouble maker. At work, when something goes wrong, we can take a guess as to who the cause of it was. He's a young recruit to our IT department, and he can cause quite some havoc to our directory. He's a good boy, though. His house plants are all alive because of him. Oh, right! Originally we accepted him into the Finance department because he was good at math, but it turns out he was really square about his methods, so we put him in IT instead. Good lot that did us, huh? Anyway, where was I... ah, yes- even though he's in IT now, his behavior from Finance stuck- I guess he's really set in his ways... something we should have checked for before we hired him.
Okay, I think that was enough of an introduction... so, were you listening?
Were you really? Then, what's his name?"
His name correlates to every italicized section (as guessed in the comments)- either replacing the word or adding to the word to form a different meaning. For example, walking could become walking stick: the meaning changing from "to go" to "an aiding item".
The word that fits the bill is 4 characters in length.