It's such a simple question and it seems like there should be a simple answer. But, there isn't. Oh, I suppose if you're just talking about taking off the top inch or two, it would be harmless enough - if the clover's more than four or five inches tall. Annual clovers are annuals because they don't stand up to things like grazing pressure and mowing and other stresses because they don't have an adequate natural propagation system. Good perennial clovers spread by stolons or, for lack of a better non-technical description, surface roots. Persistent perennial clovers have dense stolon production, annuals hardly any. So, yes, there is a risk. How big a risk, I dunno.