It’s a spilt drink (4)
I believe the answer is:
asti
'drink' is the definition.
(Asti is a type of wine)
'it's a spilt' is the wordplay.
'spilt' indicates an anagram.
'its'+'a'='itsa'
'itsa' anagrammed gives 'ASTI'.
(Other definitions for asti that I've seen before include "Capital of a north-west Italian province, known for its sparking wine" , "Source of fizz" , "Piedmont wine city, SE of Turin" , "Alcohol" , "Italian white wine" .)