A "Clan Challenge" would be an invitation you set up in your own clan for one of your members to attack you.
My favorite part about this game is attacking, but when you have a shield and about an hour of free time, its not worth it to blow the shield and risk losing more resources.. and single player isnt worth it. This is a way for people to still have fun battles while holding a shield. Also helping clan members to improve..
You can make your base open for a challenge, allowing anyone in your clan to attack it. The attack on your base would be just like in matchmaking... You use up troops that you can't get back, traps will be activated, even barb king / queen / clan castle troops will deploy to fight. Results will be the same as in matchmaking... You can lose those clan castle troops, barb king/queen sleep it off.. And the attacker risks his elixir he put into his army.
The difference with this and matchmaking is you cannot loot resources. Storages would be used as containers for your "Clan Trophies", which would be what your attacker is going for.
The "Clan Trophies" are a separate ranking system inside your own clan. It ranks the members accordingly on who has obtained the most.
This would give clans new ways to promote/demote members, tell if members are involved enough, making it a requirement that you attack so many times... You could also see a W/L ratio next to each members name.
The biggest reason this would be necessary is it allows serious feedback on your base from the people you talk to all the time. Watching a replay is helpful, but don't you with you could chat with that person and ask them what they thought the weak spot was and what they would improve... This allows for members to give each other an attackers POV and tips on how to improve.
Leaving a clan resets your clan trophies, just like donations. This will make members want to stay longer and build with the clan.
Lemme know what you guys think on the idea.

