The trendetter (emphasis on the second "e") is the one who dictates the rules of fashion. Translated from English, the word "trend" means "the direction of development", and the verb "set" means "set, set". So trendsetter is the one who with his novelties sets the direction of development and fashion trends in his field. But let's look at examples of use:
Apple with its iPhones and iPads is the undisputed trendsetter in the smartphone and tablet market. Ivan Urgant became a trendetter for TV presenters, the king of entertainment shows and just an icon of style.
The trendetter is listed: Slang