Related Clues:

• Slightly cracked
• ''When is a door not a door? When it's ---''
• Not quite 2-Down
• Open slightly
• Left so as to admit some light
• Delta follower
• Clearly not locked
• Barely open
• Allowing entry
• A door that's not a door?
• Propped open
• "When it's ___" (riddle end)
• Almost closed
• Admitting a draft, maybe
• Unshut