Die Chefsache, the boss’s matter, is a matter so important that the head takes it on personally, or should. Duden gives the example er hat das Projekt zur Chefsache erklärt, he declared the project a matter for the boss. The dictionary DWDS collects uses from the press.
Klimaschutz muss Chefsache in den Staaten dieser Welt werden. — Climate protection must become a matter for the boss in the states of the world. (Süddeutsche Zeitung, 2007)
Der Wolf in Deutschland wird Chefsache! — The wolf in Germany becomes a matter for the boss! (Bild, 2019)