credit, insurance, mortgage, real estate (AmE)
Ask advice from an insurance broker.

honest (= an independent person or country that acts between two sides in a dispute)
power
He used his position to establish himself as a power broker.

act as, be

broker between
He acted as broker between the two opposing sides.

broker for
a broker for the company

Broker is used with these nouns as the object:
ceasefire, compromise, deal, peace, talk, truce