Fellow worker the French treat roughly (9)
I believe the answer is:
manhandle
'treat roughly' is the definition.
(I've seen this before)
'fellow worker the french' is the wordplay.
'fellow' becomes 'man' (fellow can mean a man).
'worker' becomes 'hand' (hand is a kind of worker).
'the french' becomes 'le' ('the' in French).
'man'+'hand'+'le'='MANHANDLE'
(Other definitions for manhandle that I've seen before include "Knock around" , "Push (someone) about roughly" , "Mistreat" , "Give rough treatment to" , "Treat roughly, or move by human effort alone" .)