As in any normal work situation, they are called to a meeting first to discuss the issue, this is done in writing and will contain the issue they are being summoned about. They are allowed someone with them. Depending on how major the issue is, whether you miss the steps, but it is normally verbal warning, first written warning, second written warning and then dismissal. Go to the ACAS website and all the information will be there. Have you tried having an informal chat with them first to discuss the issues such as a performance review or an annual appraisal? As in any situation there needs to show proof why you want to discipline the Clerk, and as mentioned before the same rules apply as for any company.