Is bossy with, when one buys drinks from (6,6)

'is bossy with when one buys' is the definition.
I know nothing about this answer so I cannot tell whether it can be defined by this definition.

'drinks from' is the wordplay.
I cannot really understand how this works, but
'drinks' could be 'round' (as in a round of drinks) and 'round' is present in the answer.
'from' could be 'o' (I've seen this in other clues) and 'o' is found in the answer.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?