Go flat out on the French excursion (3,3)
I believe the answer is:
let rip
'go flat' is the definition.
I know nothing about this answer so I can't judge whether this works.
'on the french excursion' is the wordplay.
'on' is a charade indicator (letters next to each other).
'the french' becomes 'le' ('the' in French).
'excursion' becomes 'trip' (a trip is an excursion or outing).
'le' put next to 'trip' is 'LET RIP'.
'out' is the link.
Can you help me to learn more?
(Other definitions for let rip that I've seen before include "Triple (anag)" , "Express oneself without restraint" , "Abandon restraint - allow to tear" , "Act violently" , "Sound off" .)