Set this filter to either be completely hidden, or lightly visible but disabled. Only once a different filter has been selected will this filter become available.
Hide Widget
Hiding the filter will remove it entirely until the set filter has been selected. Add the slug for the filter that needs to be selected before the hidden filter appears.
Disable Widget
A disabled filter will still be visible, but unusable until the set filter has been selected. Add text to the tooltip, or leave it empty for no text.