The phrase "important complement" means something that is needed or necessary to complete or support something else, and is considered significant or valuable in doing so. Full definition
Directed by a volunteer board of 14, the organization employs more than 100 staff with animal care, inspection specialists, outreach workers and administrative staff, augmented by a large and very important complement of volunteers. (ottawahumane.ca)
When you do this, she says, «you begin to see that not acting is a very important complement to acting, and that being still shows us the right way to act when the time is right to act.» (yogajournal.com)
«Tmall is an important complement to our existing physical and digital stores. (alizila.com)