Drilling down on the Bar Gauge, using the text, or a hidden field

Hi,
Assuming a query like SELECT feature_name, data_value FROM table in the Bar Gauge, how can I create a drill-down link that will contain the value of feature_name? Drilling down on the data_value is generally useless for my use case, I need to filter the lower dashboard by feature_name.

${__field.name} seemed like the logical choice here, but it returns blank.

Any thoughts / advice appreciated!

Cheers,

Euan.