Possible Clues:

• Uncommunicative sort
• Tightly closed shellfish
• Quahog shellfish
• Shellfish - secretive type
• Taciturn one
• Seeing that it's one-fifty in the morning, it's all shut up
• ___ chowder soup
• In the sea one might shut up at one-fifty in the morning
• Sea creature in a shell
• Blondie album - hardly way out