Where guests were forced to drink up, necking last bit of vodka? (5)
I believe the answer is:
gulag
'where guests were forced' is the definition.
(Soviet forced labour camp)
'drink up necking last bit of vodka?' is the wordplay.
'drink' becomes 'glug' (I've seen this before).
'up' says the letters should be written backwards (in down clue: letters go upwards).
'necking' indicates putting letters inside (neck can mean to swallow).
'last bit of' indicates one should take the final letters.
The last letter of 'vodka' is 'a'.
'glug' in reverse letter order is 'gulg'.
'gulg' going around 'a' is 'GULAG'.
'to' acts as a link.
(Other definitions for gulag that I've seen before include "USSR system of labour camps" , "Soviet prison camps" , "Book by Solzhenitsyn 'The . . . . . Archipelago' about detention camps in USSR" , "Labour camp in the Soviet Union" , "Labour administration" .)