Eccentric, unpaired prior to social event (7)
I believe the answer is:
oddball
'eccentric' is the definition.
(an oddball is an eccentric person)
'unpaired prior to social event' is the wordplay.
'unpaired' becomes 'odd' (synonyms).
'prior to' is a charade indicator (letters next to each other).
'social event' becomes 'ball' (I've seen this in other clues).
'odd'+'ball'='ODDBALL'
(Other definitions for oddball that I've seen before include "Weird" , "Eccentric person like uneven sphere" , "Strange person (colloq.)" , "case" , "Crank" .)