Clue: Harry a competitor in the Crucible (6)
Answer: POTTER
Explanation: Definition: Harry,a competitor in the Crucible
 Double defn: 1st: …, in J.K. Rowling's fantasy novels; and 2nd: What you might call a player who pots balls, and would be a competitor in The Crucible (Theatre), the venue in Sheffield, England, where the World Snooker Championships are held.
Is our setter a snooker player, too?