Empty pop into beer can to get one mixed drink (9)

'empty pop' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'into beer can to get one mixed drink' is the wordplay.
I cannot quite see how this works, but
'into' could be 'in' and 'in' is found in the answer.
'get' could be 'let' (letting is a kind of getting) and 'let' is located in the answer.
'one' could be 'i' (Roman numeral) and 'i' is present in the answer.
The remaining letters 'app' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?