If your base is level 7 can you be attacked?

You can be attacked if you no longer have a Peace Shield active. When you start the game you will have one for I think 5 days or until you reach a certain level. The level used to be 6 but I believe it was raised to 8.

Check if you have a bubble / shield active by viewing your base in the world map. Or tap on the base building and select the City Buffs option to see if a shield is active. You can buy or earn shields to use when needed after this time.