Former abstainer, party-goer at heart who is outward-looking? (9)
I believe the answer is:
extravert
'is outward-looking?' is the definition.
(I've seen this before)
'former abstainer party-goer at heart' is the wordplay.
'former' becomes 'ex' (prefix meaning former or onetime).
'abstainer' becomes 'tt' (I've seen this in other clues).
'party-goer' becomes 'raver' (a rave is a dance party).
'at heart' means one lot of letters goes inside another.
'tt' going around 'raver' is 'travert'.
'ex'+'travert'='EXTRAVERT'
'who' acts as a link.
(Other definitions for extravert that I've seen before include "showing off, technically?" , "Outward-looking" , "Very sociable" , "one must look out" , "Outgoing" .)