Outside Broker

Like a guest star on a TV show, or bringing a third party into your marriage. An outside broker is someone who isn't part of your company, or comes from an external situation. Meanwhile, you're bringing them in to help out in a particular situation.

It can refer to a third party who helps negotiate a deal. Your company wants to buy a smaller competitor, and an outside broker helps arrange the sale. (This type of situation comes up a lot in real estate.) Or the term can apply to a broker who doesn't hold a membership with the major exchanges.