"Beach" is a slightly ambiguous term on Pond Boss.

Is your entire sand beach above the normal water level of your pond? Or do you have sand over fabric that extends a significant distance out into the pond? That will alter the advice.

If your entire beach is "dry", then I think a clay berm would work just fine. It just needs to be far enough onshore so that there is no wave erosion on the back side of your berm.

If you are already committed to equipment for building a berm, then you might consider also landscaping the area up-slope of the beach. I would divert any water run-off from your "yard area" to avoid flows of yard debris onto the beach. That should keep your sand cleaner over time.

I don't think you would even need a water outlet through your clay berm. Any heavy rain directly onto your beach will move right through the permeable beach sand and underlayment and into your pond - without much regard to the "dam" created by your clay berm.

Good luck on your project!