The phrase "interim chief" refers to a temporary leader or head of a group or organization. They assume the role for a specific period until a permanent chief is appointed. Full definition
Served as interim chief executive officer while training was initiated throughout company. (myperfectresume.com)
He served as interim chief of staff to Boris Johnson at City Hall and is currently working with Francis Maude in the party's Implementation Unit, considering how a future Conservative Government will put its manifesto into action. (conservativehome.blogs.com)
In addition, Mr. Heins will step down as Chief Executive Officer at closing and Mr. Chen will serve as Interim Chief Executive Officer pending completion of a search for a new Chief Executive Officer. (marketwatch.com)