cropping an adjustment layer

Hello - I created an adjustment layer for a color tint.  I want to crop a circle out of that adjustment layer, so the layers beneath are not affected by the tint in the area I mask. 

I added a crop effect to my adjustment layer > created and placed a circle where I needed it to be.

Nothing.

Everything is still tinted underneath that cropped area.

What am I doing wrong?

I've attached two screenshots before and after.  

Thanks!