The French aristocrat not sentenced to the guillotine? (3,3)
I believe the answer is:
let off
'not sentenced to the guillotine?' is the definition.
(spared execution by guillotine)
'the french aristocrat' is the wordplay.
'the french' becomes 'le' ('the' in French).
'aristocrat' becomes 'toff' (toff can mean an upper-class person).
'le'+'toff'='LET OFF'
(Other definitions for let off that I've seen before include "Detonate" , "Pardon - discharge" , "Excuse from doing, or refrain from punishing" , "Go easy on" , "Discharge - absolve" .)