As disappointing as this sounds, you can't really lose fat in target areas. It does not hurt toning your arms, it will just take more time to lose the fat in not-so-desirable areas. I also have strong legs and weak arms, but I carry all my fat in my tummy. I also have these monster calves which I really want to slim down, it's hard to tell whether it is all muscle or it has a layer of fat on them. I know my father has very large calves (he calls cows lol) that he may have passed onto me.
But yeah, do as much strength training in all areas, the more muscle you have, the more fat that will be "eaten" by those muscles.