Mother can turn the French fetter (7)
I believe the answer is:
manacle
'fetter' is the definition.
(I know that manacle is a kind of fetter)
'mother can turn the french' is the wordplay.
'mother' becomes 'ma' (ma can mean mother).
'turn' indicates an anagram.
'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?" .)