No - you will not be able to claim business expenses related to income being reported on line 21 as other "one-time" income.

However, if you report the 1099-MISC income as self-employment income on Schedule C, you would be able to claim any business related expenses.

Additionally, if you have unreimbursed job-related expenses that related to your entire employment (including the line 21 sales incentive income), then you will be able to include these as a miscellaneous itemized expense under Schedule A.

Please refer to this IRS link for more information about Business Expenses