The French enjoy the smell they make and down their wee (3,7)
I believe the answer is:
bon appetit
'the french enjoy the smell they make' is the definition.
I don't know anything about this answer so I cannot judge whether it can be defined by this definition.
'down their wee' is the wordplay.
I cannot quite understand how this works, but
'down' could be 'nap' (close in meaning in sense of hairy surface) and 'nap' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'and' is the link.
Can you help me to learn more?
(Other definitions for bon appetit that I've seen before include "Do have good meal" , "Tip-top bean (anag) - waiter's words" , "Nice diner may say this" , "What may be said before a meal" .)