tenderloin

noun

• 1 [mass noun] the tenderest part of a loin of beef, pork, etc., taken from under the short ribs in the hindquarters: grilled pork tenderloin
• US the undercut of a sirloin.

• 2North American informal a district of a city where vice and corruption are prominent: every city has a tenderloin [as modifier]:the city’s tenderloin district

  [ late 19th century: originally a term applied to a district of New York, seen as a ‘choice’ assignment by police because of the bribes offered to them to turn a blind eye]