Cast getting drunk over at premiere of Shrek (4)
I believe the answer is:
toss
'cast' is the definition.
(I've seen this before)
'drunk over at premiere of shrek' is the wordplay.
'drunk' becomes 'sot' ('sot' can be a synonym of 'drunk'**).
'over' says the letters should be written in reverse.
'at' is a charade indicator (letters next to each other).
'premiere of' indicates taking the first letters.
The first letter of 'shrek' is 's'.
'sot' in reverse letter order is 'tos'.
'tos'+'s'='TOSS'
'getting' is the link.
(Other definitions for toss that I've seen before include "Flip; hurl" , "Raise a little money" , "ball" , "Ditch" , "What to do with a pancake and a caber" .)