Don't punish the French gentleman (3,3)
I believe the answer is:
let off
'don't punish' is the definition.
I can't tell whether this defines the answer.
'the french gentleman' is the wordplay.
'the french' becomes 'le' ('the' in French).
'gentleman' becomes 'toff' (I am not sure about this - if you are sure you should believe this answer much more).
'le'+'toff'='LET OFF'
Can you help me to learn more?
(Other definitions for let off that I've seen before include "Detonate" , "Discharge - absolve" , "given a reprieve" , "Don't impose penalty or allow to dismount" , "Released - shot - treated leniently" .)