The factor I'd look at to decide whether or not to keep a clover plot that's infested with grass, is cost. One the one hand, if you keep the plot, you have to buy selective herbicides two times. One for grass, another for broadleaf weeds. Those selective herbicides are expensive. Depending on how much empty space is left between clumps of clover once your herbicides work, you will likely need o buy some clover seed. For the second possible path, killing the whole plot and starting over again, the herbicides will be a lot cheaper as you can use roundup and kill everything. Since you now have bare ground over the entire area (after mowing and disking) you will need more clover seeds than the 1st option above.
I think the 2nd will end up cheaper most of the time. This is assuming you have the time and equipment to easily rework the soil and replant.
I've got a 4 acre plot of WI AlfaRack that is going the same route. It's deteriorating fast and is down to about 15% alfalfa total but it's all concentrated to one area the furthest from the house so for now I'm leaving it alone. Considering all the row crops around, it's way more alfalfa than the deer can eat even in it's diminished state.