Drink in plastic container (4)
I believe the answer is:
asti
'drink' is the definition.
(Asti is a type of wine)
'in plastic container' is the wordplay.
'in' indicates a hidden word.
'ASTI' is hidden within 'plastic container'.
(Other definitions for asti that I've seen before include "It's a (anag) - wine" , "18" , "Italian product" , "Source of fizz" , "Piedmontese white wine" .)