Crossword Genius

Hard types to crack from banks to nuclear power plants (4)

Ross

I believe the answer is:

nuts

I'm a little stuck... Click here to teach me more about this clue!

'plants' is the definition.
The answer and definition can be both man-made objects as well as being plural nouns.
Perhaps they are linked in a way I don't understand?

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for nuts that I've seen before include "balls" , "Barmy (colloq)" , "Mad (slang)" , "Bolt securers" , "Crazy (sl.)" .)

I've seen this clue in the Irish Times (Crosaire) and the Irish Times.
Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.