Clover won't choke out turnips no matter how heavy the clover is seeded. First of all, clover uses mostly different nutrients than turnips, second, clover is so slow to establish and get rooted that the turnips are usually 6" high by the time clover is an inch. I agree with @swat1018 on the full rate seeding.
P.S. Consider some radishes with that mix, in fact I'd do 75% radishes, most deer prefer radishes over turnips.