Can my combat power return after being destroyed?

Your combat power is the total of your buildings, research level and troops power levels. When you are attacked the only power you lose is troops being wounded or killed.

If troops are wounded you can heal them and get the power back. If they are killed there is sometimes an option to clone them. But if not then you just need to train more.

If you meant the base durability instead, which can drop to 0 if you are attacked and will result in your base teleporting to a new location. This will automatically regenerate on its own, although you can speed it up with diamonds.