posrednik

1. intermediary; middleman; broker
   Stan smo kupili bez posrednika. — We bought the flat without a middleman.
   Posrednik je uzeo proviziju od dva odsto. — The broker took a two percent commission.
2. (in a dispute) mediator
   Norveška je bila posrednik u pregovorima. — Norway acted as mediator in the negotiations.

In everyday speech a real estate intermediary is usually called agent za nekretnine.