So clan allies is a thing right? Why not make it a proper feature? For example a window where the leader can add clan allies. What can clan allies do? They can help out with a war even if they belong to others clans or are clanless. In short

What a clan ally can do: Earn points in wars.


What a clan ally can't do: Everything that normal members are capable of. For example they can't start wars and they don't earn xp for the allied clan when they play a match either.