Charlie may pop back for a drink (6)
I believe the answer is:
cognac
'for a drink' is the definition.
(Cognac is an example)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for cognac that I've seen before include "French brandy region" , "warmer" , "Type of brandy" , "High quality brandy" , "French town - French brandy" .)