a central cohesive source of support and stability; "faith is his anchor"; "the keystone of campaign reform was the ban on soft money"; "he is the linchpin of this firm"
If you refer to a person or thing as the linchpin of something, you mean that they are the most important person or thing involved in it. He's the lynchpin of our team and crucial to my long-term plans. the linchpin of sth the person or thing in a group, system etc that is most important, because everything depends on them (linch (11-16 centuries) (from lynis) + pin)