Re: Help needed
As others have said, either wood glue (most people recommend Original Titebond) of super glue should work. There are three reasons I recommended super glue:
1. You're bonding wood to metal. Wood glue is meant to bond wood to wood.
2. Wood glue is very thick and I question its effectiveness here. You'd have to coat the insert with a thin amount of glue and then hope that it squeezes out the top when you insert it. There's always a chance that glue gets trapped below the insert, which would make it impossible to seat completely.
3. Thin super glue has a natural tendency to wick into even the tiniest cracks, making it ideal for repairs like this.
When I work on guitars, I consider it basically standard practice to hit the edges of the neck pocket with super glue, either to fill existing pocket cracks or try and prevent them. I've also used it to fix some small stress cracks in a neck at the nut bolts and it worked great there as well.