It would seem like the clunk noise could be getting more frequent.
I have heard it also just simply reversing in a straight line.
I'm guessing, but it would seem like it happens after the car has been sitting for a while, because if you drive it for a length of time, it seems to disappear temporarily. Park the car for a while, then take off and or turn, within seconds, same noise comes back, sometimes several times in a short space of time...