The Clear blending mode edits or paints each pixel and makes it transparent. However, since layers are so useful for non-destructive editing, the only advantage I can see is it could help keep your layer management concise. Using the Behind blending mode has the same effect as painting on a layer below the existing artwork, except everything is contained within a single layer. It’s effectively the opposite of the ‘Lock Transparent Pixels’ option at the top of the layers panel, which confines editing to the opaque portions of the layer. The Behind blending mode allows you to edit or paint only on the transparent part of a layer. They can be found in the toolbar at the top of the screen whenever the relevant tools are active, within the Mode dropdown menu, or activated directly with the Shift+ALT+Q and Shift+ALT+R shortcuts respectively. Behind and Clear are two additional blending modes that are exclusive to the Brush, Shape, Paint Bucket and Pencil tools. Blending modes in Photoshop are mostly used in combination with layers, but they are also incorporated into some tool-specific options.

Photoshop blender brushes