vested interest

noun

1. 1.An indefeasible right or title, distinguished from a contingent interest, which could be defeated (i.e. cease) if a certain event occurred.
2. 2.A fixed right granted to an employee, especially under a pension plan
3. 3.A stake, often financial, in a particular outcome
4. 4.A group of people or organizations with such a stake
5. 5.An exceptionally strong interest in protecting or promoting something to one's own advantage