Suppress attacks backing the French (6)
I believe the answer is:
stifle
'suppress' is the definition.
(I've seen this before)
'attacks backing the french' is the wordplay.
'attacks' becomes 'fits' (fit is a kind of attack).
'backing' shows that the letters should be reversed in order.
'the french' becomes 'le'.
'fits' back-to-front is 'stif'.
'stif'+'le'='STIFLE'
(Other definitions for stifle that I've seen before include "Smother or suppress a feeling or action" , "Repress, choke" , "Have difficulty breathing" , "Gag" , "Part of animal's leg" .)