Since this in a UK government pension, you will be able to claim a treaty exemption for the entire amount. You will report the full amount of the pension under the social security income section and then report the same amount (as a negative amount) as other income on line 21 of your 1040. You will also need to attach a form 8843 (which is not supported by TurboTax) to a file by mail copy of your return.
I have updated my answer to include this additional information.
