Stop, about to have left whisky container (6)
I believe the answer is:
barrel
'container' is the definition.
(barrel is a kind of container)
'stop about to have left whisky' is the wordplay.
I cannot really understand how this works, but
'stop' could be 'bar' (bar can mean to stop or prevent) and 'bar' is located in the answer.
'about' could be 're' ('re' means regarding or about) and 're' is located in the answer.
'left' could be 'l' (common abbreviation) and 'l' is located in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for barrel that I've seen before include "Tube of a gun" , "full of laughs?" , "Liquor container" , "Beer/oil container" , "Hogshead" .)