The phrase "primary work" refers to the main or most important task or job that someone is responsible for. It is the primary focus of their time and effort. Full definition
She organizes small - scale curatorial projects as primary work surface. (wysingartscentre.org)
Construction preparation has begun, with primary work potentially coming in 2019. (fortune.com)
While primary work since certification has involved commercial structures, apprenticeship was completed with service provider that worked exclusively on commercial buildings. (resume-now.com)