RE: Grass and weeds in my clover
To add to what the others have said, the rhizobium bacteria may not be present in the soil or at least not in a sufficient amount to contribute to the nitrogen fixation. Using the proper innoculant when seeding would be recommended. Also, most weeds can do very well during a drought. Mowing during periods of decent rainfall will allow the clover to choke out the weeds to some extent. On the other hand, mowing during a dry period the weeds will normally come back pretty quick as the growth of the clover will be slower than the weeds. Adding nitrogen will only add to the weed problem in this condition. I prefer a 0-20-20 fertilizer with clover but normally use a 4-24-24 because it is readily available. If you haven' t used an innoculant before you might try overseeding with innoculated seed this fall.