"Top division" refers to the highest level or the most elite category within a particular group, organization, or competition. It signifies the highest level of skill, talent, or quality within that specific context. Full definition
The Black Cats recorded the longest losing streak by any English top division side this season with a 17 game spell in which they lost every single game. (caughtoffside.com)
The Dutch top division is the only Western European league among the championships with the most young players on the pitch. (football-observatory.com)
For example, all other things being equal, a Brazilian top division match is equivalent to one in the top Portuguese league. (football-observatory.com)