William IV was styled "HRH The Duke of Clarence" between his creation in 1789 and his accession in 1830
Duke of Clarence and St Andrews was a title awarded to a prince of British Royal family. The creations was in the Peerage of Great Britain.
While there had been several creations of Dukes of Clarence (and there was later a Duke of Clarence and St Andrews), the only creation of a Duke of Clarence and St Andrews was in 1789 for The Prince William, third son of King George III. When Prince William succeeded his brother to the throne in 1830, the dukedom merged in the crown.
Dukes of Clarence and St Andrews (1789)
- also Earl of Munster (1789)