Air-filled cavity in the bones of the skull (5)

I believe the answer is:

sinus

(Other definitions for sinus that I've seen before include "Cavity within a bone" , "Space in temple" , "Hollow space" , "Cavity in body (connecting to nose)" , "Air-filled cavity in one's head" .)

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.