Related Clues:

• Connects Britain and France to ghost with narrow focus
• Let nun engineer passageway
• It has a way of getting out, that underground movement built it
• Excavated passage
• Seeing problem in dream Napoleon had for invading England?
• Restricted sight
• Inability to take a wider view
• Underground bore
• Smuggling aid
• Sounds like something footballers see at start of match? It's an ability to look obsessively for a single goal!
• Narrow-mindedness
• Burrow out of half-nelson, under barrel
• Nothing can be seen at the side in this single-minded concentration
• Narrowness of viewpoint
• One in Paris boarding fast revolutionary part of Metro?