The clearing fee is the fee charged by a clearing corporation.
The fee is usually on a sliding percentage, based on a number of quantifiable criteria, such as individual trade size, daily and monthly overall volume of trades, type of security, and the degree of risk liability for the clearing corporation (i.e., ratio of how much of their capital would be at risk vs. the client firm, intrinsic risk of the security or derivative being traded), and the focus report of the client firm in question.
It's the ages old “pay to play” platform...simply given a more ambiguous title.