From Longman Dictionary of Contemporary Englishheir apparentˌheir apˈparent noun (plural heirs apparent) [countable] 1 SCLan heir whose right to receive the family property, money, or title cannot be taken away2 someone who seems very likely to take over a person’s job, position etc when that person leaves
Examples from the Corpus
heir apparent• Huston is considered the governor's political heir apparent.From Longman Business Dictionaryheir apparentˌheir apˈparent noun [singular] journalism someone who is expected to become head of an organization after the present head leavesHe is seen as heir apparent to the chief executive. 