In the WebPreferences topic in that web set the variables ALLOWWEBVIEW, ALLOWWEBCHANGE, ALLOWWEBRENAME, ALLOWTOPICCHANGE and ALLOWTOPICRENAME to the name of the users or groups that you do want to have access to it. i.e. Main.TWikiAdminGroup
-- SamHasler - 16 Nov 2004
An answer to a similar question (but regarding denying edits to all webs) is posted in DisableEditsForMaintenance
-- SteveRJones - 22 Nov 2004