Vote to pack the lot into a half bottle (6)
I believe the answer is:
ballot
'vote' is the definition.
(balloting is a kind of voting)
'the lot into a half bottle' is the wordplay.
'the lot' becomes 'all' (I've seen this before).
'into' indicates putting letters inside.
'a half' indicates taking half.
'bottle' cut in half is 'bot'.
'all' inserted inside 'bot' is 'BALLOT'.
'to pack' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for ballot that I've seen before include "Document listing voting alternatives" , "Vote or suffrage" , "Voting paper" , "Lottery to allocate (tickets) among applicants" , "System of voting secretly" .)