Injury by degrees? (4)

I believe the answer is:

burn

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

'injury' is the definition.
(I know that burn is a type of injury)

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

Can you help me to learn more?

(Other definitions for burn that I've seen before include "Small stream in Scotland" , "Go up in smoke" , "Set on fire" , "running water" , "Severely overcook" .)

I've seen this clue in the Evening Standard.

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.