Possible Clues:

• Chief Barker is the main man
• Turns up, the man upstairs took drugs with the champion boxer perhaps
• Not suitable
• Victor
• Head honcho, and a feature of 9-, 11-, 25-, and 30-Down
• Head honcho (at the kennels?)
• Champion setter perhaps
• Most important person (or winner at Crufts?)
• Master or victor like superior canine
• Informally, the master or victor