A tough nut to crack.
difficult problem
Describing something as 'A tough nut to crack' suggests a difficult problem or situation that is hard to solve. Imagine trying to open a nut that’s particularly tough to break into to reach its fruit—this is what the idiom metaphorically compares challenging tasks to.
Example Sentences
The new problem at work is a tough nut to crack.
The new problem at work is very challenging.
Negotiating the contract terms has been a tough nut to crack.
Negotiating the contract terms has been very challenging.
Convincing him to change his mind proved to be a tough nut to crack.
Convincing him to change his mind proved to be very challenging.
