The Schedule A instructions seems to give a fairly broad definition:
For purposes of line 2, commissions and fees include sales and base commissions and all other monetary and non-monetary forms of compensation where the broker’s, agent’s, or other person’s eligibility for the payment or the amount of the payment is based, in whole or in part, on the value (e.g., policy amounts, premiums) of contracts or policies (or classes thereof) placed with or retained by an ERISA plan, including, for example, persistency and profitability bonuses.