i was about to do this for you but i did mine using pass logic, i expect you want full cmos...
- - - Updated - - -
Ok had to go back to the good ole basic cmos digital book, i work more in the realm of analog. but it seems pretty simple to me, if you take a normal negative edge triggered dff made of 2 dlatches, simply break the internal net that connects the 1st dlatch Q to the 2nd dlatch D, insert an and2, make the other and2 input your clrb(clr via inverter). this will make clear bit do nothing until clk goes to 0, at this point the output will be set to 0.