When visit : virtual attack possible
What about this :
When you visit someone from your clan, the chat or the ranking : you can virtually attack them in order to know if you can beat them or not. You can only use your actual army, but you do not lose it at the end of the game, like trophees or anything else.
This can add some challenge in your clan mainly, you can know if you are stronger than your friends ! What is not possible now unless you are enough lucky to find them with the random attack.