From Longman Dictionary of Contemporary Englishldoce_284_arevolving doorreˌvolving ˈdoor noun 1 TB[countable] a type of door in the entrance of a large building, which goes around and around as people go through it2 [singular] used to say that the people involved in a situation, organization etc change often The park director position has been a revolving door for seven appointees.3 
[singular] used to say that people return to a situation, position etc often, but usually for a different reason This could mean that we end up with a revolving door Congress, in which former members return as lobbyists.
[singular] used to say that people return to a situation, position etc often, but usually for a different reason This could mean that we end up with a revolving door Congress, in which former members return as lobbyists.Examples from the Corpus
revolving door• Term limits could mean that we end up with a revolving door Congress, in which former members return as lobbyists.• Under Treadwell, the Drifters were hired hands to be ushered in and out of his revolving door.• She joins a government-media revolving door.• She walked through the revolving door into the lobby.• The revolving door between government and think-tanks is well-established.• The revolving door has begun to rotate. 