a union payroll slot - это из «The Godfather”

And then after he had “made his bones” he had received a good living from the Family, a percentage of an East Side “book” and a union payroll slot.

Что-то вроде вычета из зарплаты в пользу сторонней организации, в данном случае профсоюза.

"payroll deduction slot" means an automatic periodic deduction from a state payroll check.

+ https://www.benefitnews.com/advisers/opinion/5-ways-to-ease-the-burden-of-payroll-deduction-for-clients