Is “flatfoot” here mean a police officer? If so, why does it mean that? Or does it mean something else?
Answer from a Native speaker
Yes, you are correct, the term "flatfoot" here mean police officer. "Flatfoot" is slang that is used for police officers, especially those who have a foot patrol. It is most likely related to the large amount of walking that foot patrol police officers have to do. It is not usually used in a positive way and may be considered offensive to some people. Ex: All you flatfoots do is hand out parking tickets. You're not real police officers. Ex: I've never wanted to be a flatfoot.