Clue: Orpington vacantly hosting carnival centre presenting seven notable stars (5)
Answer: ORION
Explanation: Definition: seven notable stars
An envelope ('hosting') of RIO (de Janiero, 'carnival centre') in ON ('**O**rpingto**N** vacantly'). The constellation of Orion has many stars, but the brightest and most recognizable form the shoulders and legs (two apiece) and the belt (three).