The French stumble and speak furiously (3,3)
I believe the answer is:
let rip
'speak furiously' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'the french stumble' is the wordplay.
'the french' becomes 'le' ('the' in French).
'stumble' becomes 'trip' (synonyms).
'le'+'trip'='LET RIP'
'and' acts as a link.
Can you help me to learn more?
(Other definitions for let rip that I've seen before include "Hasten" , "Talk aggressively" , "Act without restraint" , "Speak violently - allow to tear" , "Behave without restraint" .)