The French stand to spend up big (4,3)
I believe the answer is:
lash out
'spend up big' is the definition.
I can't judge whether this defines the answer.
'the french stand' is the wordplay.
'the french' becomes 'la' (one of the French words for 'the').
'stand' becomes 'shout' (I can't explain this - if you can you should believe this answer much more).
'la'+'shout'='LASH OUT'
'to' is the link.
Can you help me to learn more?
(Other definitions for lash out that I've seen before include "spend a fortune" , "React violently" , "severely run down" , "Recklessly spend" , "Spend extravagantly" .)