During a social event, drinking very early (2,7)
I believe the answer is:
in advance
'early' is the definition.
(similar in meaning)
'during a social event drinking very' is the wordplay.
'during' becomes 'in' (e.g. during February means in February).
'social event' becomes 'dance' (a dance is a type of social event).
'drinking' indicates putting letters inside (inserted letters are consumed or drunk).
'very' becomes 'v' (abbreviation).
'dance' placed around 'v' is 'dvance'.
'in'+'a'+'dvance'='IN ADVANCE'
(Other definitions for in advance that I've seen before include "Before the event" , "early" , "Beforehand - can invade accordingly (2.7)" , "Ahead in place or time" .)