I used clover for cover crop last year, as the drought the year before cut severely the available hay for mulch. Once the clover reached a certain height and the plants got so big, I was unable to stay on top of the weeds and the huge are was a horrible mess.
I have used clover cover crop before due to mulch shortage, but this was the worst mess! So don't count on it stopping weeds well, unless you pull the weeds.
Just about everything you see green here (except leeks in foreground) are volunteers or weeds gone wild. With the soil balanced, things do really well, and that includes weeds.
RE: My Part In The "One Straw Revolution"