Possible Clues:

• *Four-time heavyweight champ nicknamed 'The Real Deal'
• '90s heavyweight champ
• 1 across in which to find sacred cow?
• Did he have a bit part against Mike Tyson in a heavyweight war?
• Oh I'll defy for a boxing master
• Did he play a bit part with Tyson?
• The Real Deal
• Hide folly, anagram
• 8-Down opponent