Inspect
Investigate
If a tree is growing out of a top hat you need to inspect it to find out why and how this happened. You should probably investigate the area too. I mean, how could a tree grow out of a top hat anyway? Seems suspicious.
さ
None
None
As you inspect the tree, you pick up a saw (さ) and start cutting it. You need to investigate how the tree and the top hat are connected, and a saw is the only way to do it properly.