Protect defender in the NFL? (5)

I believe the answer is:

guard

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

'protect' is the definition.
(I know that guard is a more specific form of the action protect)

I don't understand the rest of the clue.

(Other definitions for guard that I've seen before include "Protect(or)" , "Sentinel" , "Screw" , "One keeps watch" , "Shield" .)

I've seen this clue in The Sun.

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.