Possible Clues:

• Scottish author with the ultimate in writer's block?
• Something that obstructs black bird, cutting head
• See 9
• Scottish writer given right to build obstacle
• Roadblock or 2-Down
• It's a stumbling block for butcher's rare rib
• Wall, partition
• Protective rail
• Writer dramatically going over river dam
• Pub on river that's at first road block