Related Clues:

• Heavily populated
• Like urban populations
• Crammed in
• Hard to see through
• Far from 22-Down
• Overgrown
• Hard to see through, as fog
• A little on the slow side
• Not sparse
• Not Mensa material
• Compacted
• Like thickets
• Not the sharpest pencil in the box
• Not very sharp
• A few bricks shy of a load