It's used for turning a French article to an English one (5)
I believe the answer is:
lathe
'it's used for turning a french' is the definition.
I can't judge whether this defines the answer.
'article to an english one' is the wordplay.
'article' becomes 'the' (the 'definite article' part of speech).
'to' says to put letters next to each other (I've seen this in other clues).
'an english' becomes 'l' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'one' becomes 'a'.
'l'+'a'='la'
'the' after 'la' is 'LATHE'.
Can you help me to learn more?
(Other definitions for lathe that I've seen before include "Means for turning" , "Wood-turning machine" , "Turning implement" , "Machine for cutting, drilling or polishing" , "Turner's machine" .)