It's hammered home (4)

I believe the answer is:

nail

(Other definitions for nail that I've seen before include "Fasten - detect and expose" , "Steel pin used by carpenters" , "Hammered individual" , "it needs hammering home" , "Metal spike with head" .)

I've seen this clue in The Guardian.

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.