Possible Clues:

• Additional security feature for war historian
• Lets out that one lets in
• Confesses or allows to enter
• The dam being broken, it's letting things in (6)
• One does not deny that one lets this in
• Owns up or grants entrance to
• Gives access to passages round mountain top
• Allows to pass
• ... announcements about American university's grants
• Reluctantly discloses