Informed about article ahead of social event (2,3,4)
I believe the answer is:
on the ball
'informed' is the definition.
(I've seen this before)
'about article ahead of social event' is the wordplay.
'about' becomes 'on' (as in a book 'on' a certain topic).
'article' becomes 'the' (the definite article in English).
'ahead of' says to put letters next to each other (some letters go in front of others).
'social event' becomes 'ball' (I've seen this in another clue).
'on'+'the'+'ball'='ON THE BALL'
(Other definitions for on the ball that I've seen before include "concentrating here during Lottery draw?" , "Informally alert or competent, like good soccer player" , "footballer puts boots here" , "umpire may look for suspicious scratches here" , "Intelligent" .)