Crankitup, if it's Burr Medic just spray with MCPA of Dicamba, and then spray again in 14 days time, this should get rid of most of the Burr Medic, then aerate it and then spread some fertiliser and water in this will bring your lawn up nice. Yes it is in the Clover family but it is a prodigious seeder, where Clover is more to do with lack of Nitrogen in the soil. If you feed the Burr Medic you may end up with a major headache next year.