Spoil container with one drink (7)
I believe the answer is:
martini
'drink' is the definition.
(martini is a kind of drink)
'spoil container with one' is the wordplay.
'spoil' becomes 'mar' (synonyms).
'container' becomes 'tin' (tin is a kind of container).
'with' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'mar'+'tin'+'i'='MARTINI'
(Other definitions for martini that I've seen before include "Alternative name for Simone Memmi, pre-Renaissance Italian painter" , "Type of Italian vermouth" , "alcoholic drink" , "In glass, one's dry" , "Italian drink" .)