This command will wipe the entire access list of a user. To view an access list you would type /msg nickserv access list <nick>.
Example:
/msg nickserv access wipe WebMaster
Sometimes an access list is so badly set that it is simpler to wipe all of the entries and add in some properly set entries than to individually delete the poorly set entries. This is true when the person has entries that are far too wide, such as *@* or several entries that are too specific, showing a lack of understanding of how to use wildcards. Another problem that sometimes occurs is that users add entries that include a !, because they think that access lists work like bans. Access lists are very similar, but you do not need to specify the nickname, so you should not have an exclamation mark in an access list entry. Access lists that are too wide will give too many people access to the nick, and ops in rooms where that nick has ops. Access lists that are poorly set will require the nick owner to identify more often, and they may get affected by protect if it is set on.