Up endlessly making wine (4)
I believe the answer is:
asti
'wine' is the definition.
(I've seen this before)
'up endlessly' is the wordplay.
'up' becomes 'astir' ('astir' can be a synonym of 'up').
'endlessly' means to remove the last letter.
'astir' with its final letter removed is 'ASTI'.
'making' acts as a link.
(Other definitions for asti that I've seen before include "It's a (anag) - wine" , "Italian wine - (then change a letter for ...)" , "Italian white wine" , "Source of fizz" , "Capital of a north-west Italian province, known for its sparking wine" .)