middleman

(noun) someone who buys large quantities of goods and resells to merchants rather than to the ultimate customers. Synonyms: jobber, wholesaler.

(noun) the performer in the middle of a minstrel line who engages the others in talk. Synonyms: interlocutor.

(noun) a person who is in a position to give you special assistance. Synonyms: contact. Example: "He used his business contacts to get an introduction to the governor."