Blurred Edges?

You're looking for a "vignette" effect (might help in your search). I'd bet, dimes to donuts, that one of your BCC blurs has masking built-in, which would enable you to limit where the blur effect is applied within a frame.

Barring that, you could try this:

1. Stack another instance of your clip on top of the original.
2. Apply a blur of your choice to the lower clip, and set the blur to taste.
   
3. Apply the Circle effect to the upper clip. Tweak the following settings:
   1. Set Blending Mode to "Stencil Alpha"
   2. Increase Radius as necessary
   3. Apply Feathering as necessary to soften the edges of the matte
   4. Position the circle matte using the Center property
4. You could also use Levels, Curves, or some other CC effect on the background blurred clip to darken/lighten it, if you like.