Possible Clues:

• Unloyal
• It's not true that it could be made safe around fifty
• River's direction can be deceptive
• Answer choice on a test
• Footballers and economists shouldn't play it
• River Swale's banks treacherous
• What "F" means on a test
• ___ positive
• One of two options in five squares in this puzzle
• Note London School of Economics is wrong