Also, ignoring it last year. Perennial weeds don't spring up instantly--they creep. You didn't see them last year--because you didn't want to. Deal with them early--before they get out of hand--when the patches of infestation are still small.
And clover is good for the soil. Clover is a legume. It produces its own nitrogen by fixing it from elemental nitrogen in the air. Good for the soil and the grass. The grass will be greener. The white flowers should appear for only about four weeks when the temperature first hits 80 in the spring. Cut short when the flowers appear, and new ones will return only slowly.