Secure with a key (4)

I believe the answer is:

lock

(Other definitions for lock that I've seen before include "Security device - bit of hair" , "Tress; fasten" , "Get stuck in" , "Become immoveable" , "Tress of hair" .)

I've seen this clue in the Universal and the USA Today.

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.