Hi Brijesh,
Looks like the problem is that you are trying to retrive custom field on parent page type. If that is the case, you must combine you query (macro method) with 'WithAllData' method. Try something like this:
{% Documents.WithAllData.Where("NodeAliasPath='" + CurrentDocument.Parent.NodeAliasPath + "'")[0].GetValue("TOC") |(identity)GlobalAdministrator%}
This should solve your issue. You can modify where condition how ever suits you best, but 'WithAllData' is necessary.
Best regards,
Dragoljub