For the love of all things holy... how do I remove the stock sound effect from an individual track?

About to pull my hair out, please help! And please don't yell "this has been answered before" -- I've been trying to find the solution and keep hitting dead ends.

This should be simple: if I apply a preset sound effect from the stock library, like Library > Acoustic Guitar > Echo Strum and I later want to remove that effect, how do I do that?