If a place is seedy, it is dirty, not safe, and maybe a little bit scary.
The word seedy makes people think of bad places, like dark alleys or old buildings.
Examples:
The seedy alley was dark and scary.
I don't want to go to that seedy part of town.
The seedy hotel was not a good place to stay.
The seedy old house looked like it might fall down.
In the seedy part of the city, you have to be careful.
The seedy bar was not a nice place to be.