Buttocks (euphemistically) (8)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
derriere
(Other definitions for derriere that I've seen before include "A French backside or buttocks" , "Seat" , "(French?) behind" , "Fourteen down's [FRENCHMAN] behind" , "One's backside in France" .)