Not knowing what plant hardiness zone you are in, I will just add that in general, you don't want to reseed clover in the spring. It is much more difficult to get clover established with warm season weeds and grasses than it is in the fall.
If you have a plot of clover that has actively growing grass, you can spray it with a grass selective herbicide. You will get a better kill of the grasses if you spray young grasses rather than mature grasses. You won't have any issues with Clethodim impacting clover germination.