"Has anyone ever been the Clerk and then become a member of parliament?"

The Senate and the House of Representatives each has a Clerk, who is the senior parliamentary officer for that house of Parliament. The Clerks have a thorough understanding of the rules of the Senate and House—called the Standing Orders—and are the only non-elected people who regularly speak in Parliament.

 

Being appointed Clerk of the Senate or House of Representatives is usually the high-point of a long and distinguished career in public service and, so far, no Clerk has ever gone on to become a member of Parliament.

However, there is nothing to prevent a retired Clerk from standing for Parliament in the future, so long as they fulfil the nomination requirements.