Retiring extrovert? (8)
I believe the answer is:
outgoing
I believe this clue is a double definition.
'retiring' is the first definition.
(similar in meaning)
'extrovert?' is the second definition.
(both can mean social)
(Other definitions for outgoing that I've seen before include "Friendly and sociable" , "Extrovert" , "At ease in talking to others, extroverted" , "Departing" , "Expenditure" .)