Plunging chair for offenders (7,5)

I believe the answer is:

ducking stool

(Other definitions for ducking stool that I've seen before include "Chair once used to punish offenders" , "Offenders took a dip in it" , "Chair for submerging offenders" , "Old form of punishment using water" , "Old instrument of punishment, using a chair and water" .)

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.