Meta class has a description field, but it is used as a meta description.
There are two hooks in the price-drop.tpl template: displayPricesDropTop and displayPricesDropBelow.
In "tbhtmlblock" module, you would need to add support for these hooks and use this module to enter these descriptions.
By modifying this module, you could immediately add support for the following hooks:
- displayNewProductsTop and displayNewProductsBelow,
- displayBestSalesTop and displayBestSalesBelow (not in the template, you also need to add it in the theme template).
By the way, this "tbhtmlblock" module is incorrectly constructed because it does not work in multishop mode and it should be properly fixed.