Carelessly rated the French lever (7)
I believe the answer is:
treadle
'lever' is the definition.
(I know that treadle is a type of lever)
'carelessly rated the french' is the wordplay.
'carelessly' indicates an anagram.
'the french' becomes 'le' ('the' in French).
'rated' is an anagram of 'tread'.
'tread'+'le'='TREADLE'
(Other definitions for treadle that I've seen before include "Related (anag.)" , "Rocker in a factory" , "Foot-operated lever" , "Foot lever that works a machine" , "Dear, let a foot lever emerge" .)