apple cart

noun

ap·​ple cart ˈa-pəl-ˌkärt 

variants or less commonly applecart

: an established or expected plan, system, situation, or undertaking that may be disrupted or terminated

She … wanted to kind of do things her way without turning the apple cart completely upside down.

—Ron Wood, quoted in Sports Business Journal

see also:

upset the apple cart

Word History

First Known Use

1788, in the meaning defined above