From Longman Dictionary of Contemporary Englishsitting tenantˌsitting ˈtenant noun [countable] British English SCLsomeone who lives in a rented house or flat, especially when this gives them legal rights to stay there
Examples from the Corpus
sitting tenant• A sitting tenant who came with the greenhouses ... and is doing his bit to keep down the slugs.• Like these events in Knowsley North, where the sitting tenant is George Howarth.From Longman Business Dictionarysitting tenantˌsitting ˈtenantLAWPROPERTY a tenant that cannot be forced to move if a building is sold → tenant 