I wouldn't be sure if I told you anything, best thing to do is ask your co op people. I tried to make a pure clover plot once, and I talked to a co op crop advisor and he said there ain't much out there they won't ding it up some. When I did turf management a few years ago, a 2-4D would knock it back some, but usually would take us two separate applications to kill it. A 2-4D is designed to kill broadleaf weeds, and that includes a few different clovers. Controlling the grassy weeds should be easier, just find a selective herbicide that targets grasses, the best was MSMA, but they quit making it, and it is possibly illegal now, not sure though.
I would think if you asked the right guy, that they would know of something. Clover is too popular to not have a selective herbicide to spray in clover fields.