How to empty DropdownSearch widget after click?

At this moment when I click on an element of the DropdownSearch, I am able to execute a client action and do application specific work and this is just fine.
However I would like to have a better user experience by removing the chosen element from the searchbar. In this way it is obvious for the user that (s)he can choose another item in the dropdown.

One thing I already tried:
Keep a 'Dropdown structure' variable in the 'SelectedItem' property and make it NULL when an item is clicked. This does not work.

TLDR: How can I achieve this 

instead of this 

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