P T —, showman who formed a circus with rival J A Bailey in 1881 (6)
I believe the answer is:
barnum
(Other definitions for barnum that I've seen before include "US showman who popularized the circus" , "Bailey's circus partner, d. 1891" , "Man who was responsible for entertaining" , "US creator of "The Greatest Show On Earth"" , "With Bailey, he ran a famous circus" .)