Mother can turn the French fetter (7)
I believe the answer is:
manacle
'fetter' is the definition.
(manacling is a kind of fettering)
'mother can turn the french' is the wordplay.
'mother' becomes 'ma' (ma can mean mother).
'turn' indicates anagramming the letters.
'the french' becomes 'le' ('the' in French).
'can' is an anagram of 'nac'.
'ma'+'nac'+'le'='MANACLE'
(Other definitions for manacle that I've seen before include "Handcuff" , "Metal shackle" , "Shackle on the wrist" , "Fetter" , "restricting at the cuff?" .)