Yes, Backup Withholding may be reported under Deductions & Credits >> Other Income Taxes Paid.
The easiest way to find this section of TurboTax is to use the Search box at the top right side of the TurboTax header. Click on the magnifying glass, type in "estimated taxes paid", and hit Enter. The first result should be "jump to estimated taxes paid". Click on this link to go directly to the input screen for this topic.
Report the amount that was withheld under Withholding not already entered on a W-2 or 1099 under Other Income Taxes Paid in 20XX (see screenshot below - click to enlarge).
This withholding tax will be included with other income taxes you paid and will be applied to the taxes you owe on your tax return (Form 1040 Line 64).