I suspect -- but am not positive -- these are trichogramma wasp pupae on clover eating butterfly or moth caterpillar. The larvae emerged from the demolished caterpillar and pupated on the leaf.
If curious, I would put in a paper towel lined jar with rubber banded paper towel lid and see what comes out. (I am!
If they are wasps, then yes, they are beneficial (even if these might have eaten a nice butterfly caterpillar)
A fairly common butterfly to use clover as host plant would be a Sulfurs -- yellow butterflies... Have you seen any around? There's another one I'm thinking of bunt can't remember it.... Hmm I guess the other ones I'm thinking of must be Hairstreaks and Blues (tiny silver grey butterflies with tiny tails).