Yes you can fertilize, remember, you only need P & K not N, because the clover makes it's own. If you have moss, you generally have too much moisture and low ph. Lime that area to raise the ph and get something else going in there to soak up the excess moisture. Alsike clover doesn't mind wet feet. Do you know the ph of that plot from your soil test? Chances are the whole plot could use some lime and that would help "free up" fertilizer that is already in your soil for use by your clover.