Popular presenter of the W.W.N. (Wizarding Wireless Network) program Witching Hour (FW).
Glenda is similar to Glinda, the name of the Good Witch in The Wizard of Oz.
Chittock is possibly a combination of "chit-chat" and "talk," which would be appropriate for a radio host.
Glenda appeared as the Wizard of the Month on JKRowling.com for October, 2004 (JKR).