The term 'borough boss' refers to a mayor of a borough in New York City. The solutions to the crossword are MAYOR (5 letters), BRONX (5 letters), POOLE (5 letters), and QUEENS (6 letters). The mayor of the BRONX is known as the BRONX Borough Boss, the mayor of Queens is known as the Queens Borough Boss, and the mayor of Staten Island is known as the Richmond Borough Boss. The mayor of Manhattan is known as the Mayor of New York City.