Slight clunk on front end when going over a sleeping policman

I've noticed when I go overthrew wide sleeping policeman on my rd that the front seems to have a clunk sound . It's just passed an mot done 60k and feels fine with no odd noises when driven but as i ride up over a lump like a sleeping policeman you can feel a sort of clunk / play in the feedback you get from the steering wheel. I've wiggled the front wheels but no knocks wondered if it's a arb bush or something like that,?