Photoshop’s Crop tool works on the whole canvas, not an individual layer. To crop just one layer, use one of these layer-based methods:

• Non-destructive: Add a layer mask to the layer and mask out the parts you don’t want. This hides the outside area without permanently deleting it.
• Destructive: Use the Rectangular Marquee to select the area you want to keep, then either:
  • Invert the selection and delete the outside area, or
  • Copy the selected area, delete the original layer, and paste the copied portion onto a new layer.

If the layer extends beyond the canvas, copying the selected area to a new layer can be the cleanest approach.

So: you can’t directly “crop” a single layer with the Crop tool, but you can achieve the same result with a mask or a selection-and-delete/copy workflow.