Right away? Bad form! You won't like how that turns out.
If cut several weeks after the application, they should not be a problem. You should be mulching those grass clippings before throwing them on other plants, anyway. Fresh cut, then mulched for several weeks would not work, either.
I would cut before you apply to open the weeds so the herbicide can quickly get into the system. Also there should be rain fast time that you should apply before it rains or you irrigate.