The crossword solution for the term 'Prince, to a throne' is 'HEIR', which has 4 letters. An HEIR is someone who is entitled to inherit the throne of a monarchy upon the death of the current monarch. Heirs are typically the eldest son or daughter of the current monarch, but can also be other relatives such as siblings, uncles, aunts, and cousins. In some cases, the HEIR may be chosen by the current monarch.