Competitor is a synonym of Rival. Champion is a type of Rival. Champion is a synonym of Defend. you would Fence because Defend. 
Divorce is a synonym of Separation. Separation is related to Door. 
Competitor <--Synonym--> Rival <--IsA-- Champion <--Synonym--> Defend <--MotivatedByGoal-- Fence 
Divorce <--Synonym--> Separation <--RelatedTo--> Door 