In French, sent back dessert to finish (3,2)
I believe the answer is:
end up
'finish' is the definition.
(ending up is a kind of finishing)
'in french sent back dessert' is the wordplay.
'in french' becomes 'en' ('en' can be French for 'in' e.g. en France).
'sent back' says the letters should be written backwards.
'dessert' becomes 'pud' (pud is a kind of dessert).
'pud' written backwards gives 'dup'.
'en'+'dup'='END UP'
'to' acts as a link.
(Other definitions for end up that I've seen before include "Eventually find oneself" , "Ultimately become" , "finish ahead" , "on your head, maybe" , "Turn out" .)