The phrase "good brief" means that someone has provided clear and concise instructions or information, making it easier for others to understand and act upon. Full definition
Along with their first - place finish, the team earned the first - place award for best oral argument and the second - place award for best brief. (kentlaw.iit.edu)
The team placed fourth overall in the national finals and had the third - place best brief. (kentlaw.iit.edu)