"Farewell, mon ami" (5)
I believe the answer is:
adieu
'farewell mon ami' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for adieu that I've seen before include "Cheerio" , "Ciao, in French" , "Goodbye, monsieur" , "I'm away (in France?)" , "Farewell (French)" .)