How do you link an adjastment layer to the underneath layer only

Hi, many years ago I used to link an adjustment layer to the underneath layer. That was done with option click or command click I don't remember. Certainly not control click. This is important when your underlying layer is a patch, a small portion because you don't want the effect on the whole image.

In this case my patch is in layer 1. For "patch" I mean a portion of layer 0 brought up to layer 1 with Command C, Command V. The resulting link was a rght angle arrow pointing from the A Layer to the underlying layer. Doing the above I don't obtain anything. Thanks