There's no real ideal way to do this at the moment...
The closest you can get is to build some logic into a calculated metric using the If function with the Greater Than / Greater Than or Equal function to look for value above your threshold, then if it's high enough calculate the click rate, otherwise set the rate to a static 0.
Those items will all still be returned to your freeform table, but at least when you sort high to low, the items that don't make the threshold will all be at the bottom of the list (or on subsequent pages).
Something like this:
You can replace "Page Views" with the metric you need in the IF/GTE statement, and with your Rate Calculation in the "value_if_true" area. You will notice that I just used some static values of 500,000 (change to your threshold) and 0.