Related Clues:
- Known by only a few
- Undercover
- Something given, often not to be passed on
- Inner
- Whispered thing
- Hidden, as eight related pieces in the grid
- For only a select few
- Nothing to write home about?
- Known to few
- Cloak-and-dagger
- Like some documents
- Like some handshakes
- Secret sort of soldier
- It's not to be told
- Confidential, not to be revealed