The term 'Heir Apparent' refers to the person who is first in line to succeed a monarch or other hereditary ruler. This person is usually the ELDEST child of the current ruler. In crossword puzzles, the two most common solutions for this term are 'ELDEST' (6 letters) and 'Crownprince' (11 letters). ELDEST is used to describe the oldest member of a family, while Crownprince is a title given to the heir apparent of a monarchy.