Lie has nothing on the French weaknesses (7)
I believe the answer is:
foibles
'weaknesses' is the definition.
(I've seen this before)
'lie has nothing on the french' is the wordplay.
'lie' becomes 'fib' (fibbing is a kind of liing).
'has' means one lot of letters goes inside another.
'nothing on' becomes 'o' (I've seen this in other clues).
'the french' becomes 'les' (plural form of 'the' in French).
'fib' placed around 'o' is 'foib'.
'foib'+'les'='FOIBLES'
(Other definitions for foibles that I've seen before include "Weaknesses" , "Minor character faults" , "Quirks" , "Fob lies about harmless peculiarities" .)