Collocations for middleman - noun

act as, be
bypass (AmE), cut out, eliminate
Some factories have cut out the middleman and sell their products directly to customers.

through a middleman
The company sells through a middleman because it does not have its own sales force.

middleman between
advisers who operate as middlemen between savers and borrowers.

middleman for
He acts as a middleman for companies seeking contracts overseas.