Former treasure, right raver (9)
I believe the answer is:
extrovert
'raver' is the definition.
(raver can mean a very social person)
'former treasure right' is the wordplay.
'former' becomes 'ex' (prefix meaning former or onetime).
'treasure' becomes 'trove' (trove is a kind of treasure).
'right' becomes 'rt' (abbreviation as in Rt Hon- the Right Honourable).
'ex'+'trove'+'rt'='EXTROVERT'
(Other definitions for extrovert that I've seen before include "Person who is more interested in the world than the inner self" , "party animal" , "he's turned out" , "A lively sociable person, always up front" , "party type" .)