AccountExtension.cls

public class AccountExtension {

    private ApexPages.StandardController standardController;

    public AccountExtension(ApexPages.StandardController standardController) {
        this.standardController = standardController;
        this.standardController.addFields(new List<String>{'Name'});
    }

    public Pagereference reverseName() {
        Account record = (Account) standardController.getRecord();
        record.Name = record.Name.reverse();

        update record;

        return this.standardController.view();
    }
}