Hello Zerop, LWC is unfortunately not aware of who is in what clan, but PreciousStones is.
For cases where you want everyone in a clan to be able to access a chest, for instance, we tell people to make sure the chest is in a PreciousStones protection field and then either not lock the chest at all, or make it a "public" lock (with /cpublic and clicking the unlocked chest). If it's a publicly-locked chest, that would allow anyone who can access the PreciousStones field (by default: you and your clan members) but they would not be able to remove the chest. If it was not locked at all, allowed members would be able to interact with it as if it were not protected. Publicly-locked or unlocked though, all non-clan-members would not be allowed to interact with the chest at all.