| Clue | Source | Date |
|---|---|---|
| Hard, impenetrable (10) | ||
| First male worker accepted by English is unbreakable (10) | ||
| A woman keeping a note and cash, resisting all requests | The Guardian Cryptic | 06 Sep 2023 |
| Fully firm | Newsday | 18 Mar 2023 |
| Immovable plug a worker discovered in pit | ||
| A US woman eclipsing rival before end of election, very tough | The Times Cryptic | 22 Oct 2015 |
| Extremely hard to wrongly detain a fellow inside | ||
| Very hard old gaoler opposed to one slipping over | ||
| Hard | ||
| Unyielding | ||
| Impenetrable. | ||
| Immovable. | ||
| Firm. | ||
| Unyielding. |