Possible Clues:

• Stop at entrance - you get licence inside
• Transparent case leader of investigation dropped
• Head's not empty — is that clear?
• It's clear the invalid is disheartened
• This leather has a glossy varnished surface
• Unconcealed
• Lincoln is the only U.S. president to have one
• Obvious trap that's snare for rook coming back
• One shuns ill person, getting clear
• The answer is obvious. Protect it by law