You French, rubbish backing train (5)
I believe the answer is:
tutor
'train' is the definition.
(I've seen this before)
'you french rubbish backing' is the wordplay.
'you french' becomes 'tu' ('you' in French).
'rubbish' becomes 'rot' (both can mean nonsense).
'backing' says the letters should be written backwards.
'rot' reversed gives 'tor'.
'tu'+'tor'='TUTOR'
(Other definitions for tutor that I've seen before include "Master" , "trainer" , "School" , "Teacher (often private)" , "Trout (anag)" .)