It's possible that it's a misinterpretation or a regional slang term.
Here's why it's likely not a standard expression:
* "Nuts" usually implies someone is crazy or foolish.
* "Foxes" are typically associated with cleverness, cunning, and resourcefulness.
These two concepts don't usually go together in a straightforward way.
If you heard someone use this phrase, it's best to ask them for clarification to understand what they meant.