Possible Clues:

• Media maven Marshall
• Marshall __, Canadian philosopher credited with the phrase, 'the global village'
• Marshall in LA worked with 25
• Marshall ____ (futurist)
• "Don't get me wrong constructing crosswords is fun. What takes forever is the ___"
• "Canadians are mildewed with caution", he said
• Marshall -, communications theorist (The medium is the message)