Experts and BHG readers answer.
'semi-weeds in lawn
Use a two- or three-way broadleaf weed herbicide spray for clover. There's no other good way to remove it. You will often need to follow up with a second treatment in 2-3 weeks to finish the job. It is a little easier on your lawn if you wait until the weather cools a bit. Early fall is ideal.
Violets are very tough. Try the herbicide, but don't get your hopes up. I have found they're not that tough to remove by hand. Depends on how much of it you have, obviously. But often, they are completely unaffected by herbicides, so removal by hand may be the only option.
Be sure to follow all product instructions whenever you use chemicals.