The phrase "major reshuffle" means a significant rearrangement or reorganization of something, like a team, a company, or a government. Full definition
The first deputy mayor of New York City, Anthony Shorris, said he's leaving (voluntarily) the administration, a move that marks the first major reshuffling of Mayor Bill de Blasio's inner circle as he prepares for a second term. (nystateofpolitics.com)
When Cameron conducted his first major reshuffle in July 2014, it was only Conservative ministers who were moved. (democraticaudit.com)
British prime minister David Cameron conducted the first major reshuffle of his coalition government on 4 September 2012. (en.wikipedia.org)