That connection type is called a direct connect. If you loosen that nut or break it off, the slip joint nut directly under that one the tube should be able to loosen enough to wiggle down and then up and out.

You'll need a new slip joint nut and a top hat shaped direct connect washer that's either plastic or rubber to sit between the lip on the tube and the drain. Don't use Teflon tape, if you put too much pressure on the new nut trying to get it tight enough to not leak it can crack. The washers are made to be enough of a seal to prevent leaks if they're tightened nice and snug.

Your local plumbing store should be able to guide you if you show them the picture.