Spoil drink that's made by the border (6)
I believe the answer is:
margin
'the border' is the definition.
(synonyms)
'spoil drink that's made by' is the wordplay.
'spoil' becomes 'mar' (synonyms).
'drink' becomes 'gin' (gin is a kind of drink).
'that's made by' is a charade indicator (letters next to each other) (letters written or made by another set of letters).
'mar'+'gin'='MARGIN'
(Other definitions for margin that I've seen before include "Space at edge of page" , "Edge; room for error" , "Bland space around text" , "Boundary line or the area" , "Edge or space for error" .)