Nuts only 40% chewed (4)

I believe the answer is:

mast

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

'nuts' is the definition.
(mast is the nuts of forest trees)

I don't understand how the remainder of the clue works.

(Other definitions for mast that I've seen before include "Sail carrier" , "One carries the sails of a ship" , "nuts and seeds" , "Pole supporting ship's sails" , "Large transmitter" .)

I've seen this clue in The 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.