Hi,
spontaneous I would suggest storing a reference to your actor (that gets the outline) somewhere where it is accessible from everywhere (like GameMode or GameInstance). If you click a new actor you check if it is the same or a different. If it is a different you destroy your outline. I guess the best approach is anyway to not always spawn and destroy your outline actor. Just disable it and if you want to display it, enable it and place it on the right location.
Hope I understood you problem and my answer will help you.
Cheers