A French farewell to God (5)
I believe the answer is:
adieu
'a french farewell' is the definition.
(I've seen this before)
'to god' is the wordplay.
'to' becomes 'a' (I can't justify this - if you can you should give a lot more credence to this answer).
'god' becomes 'dieu' (I've seen this before).
'a'+'dieu'='ADIEU'
Can you help me to learn more?
(Other definitions for adieu that I've seen before include "All the best" , "Ciao, in French" , "farewell message" , "Fare thee well!" , "Cheerio" .)