The phrase "straight fight" means a fair and direct competition or conflict between two people or groups, without any tricks or complications. Full definition
The game uses a simple and straight fighting mechanic where fun is the important thing. (kickstarter.com)
He lost to Matt Mitrione by TKO last June in his Bellator debut, but he previously won five straight fights after three consecutive losses. (tsn.ca)
Romero (+130 to win this fight) had won eight straight fights before meeting Whittaker in a bout for the interim championship at UFC 213. (sbnation.com)