Yeah, this is the downside of chipboard: it's only kinda-repairable at best.

Wood glue + pressure is a good first step. Wipe the edges carefully to minimize seepage out the edges. After it drys you can rub a dark brown crayon around the edges to get wax into any visible seams to hide them.

To reassemble, you'll want to consider if you can use something like T-nuts. Or, as the other poster suggested, something stronger behind that you actually screw into. Consider that if this part was this weak, probably so are any other similar attachment points. So maybe while you're at it you could reinforce other places similarly.