at the top of the tree
In the highest position or level in an organization, field, etc. Primarily heard in UK. Don't expect to be at the top of the tree right out of college. It takes time to work your way up. With her new promotion, Jill is now at the top of the tree as CEO. Man, I can't wait till I'm at the top of the tree around here. All I do now is make copies and get coffee for people!
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