This usage is to indicate purpose, it is short for "~ためには". In context "In order to fill the void of the victim's heart, love is the best!"  
「心のスキマを埋めるためには―恋がいちばん！」

The ～ため part of ～ために

[Read more here][1]

  [1]: https://www.imabi.net/inorderto.htm