Because it hinges on the wine (4)
I believe the answer is:
asti
'the wine' is the definition.
(Italian wine)
'because it hinges' is the wordplay.
'because' becomes 'as' (I've seen this in other clues).
'it' becomes ''t' (abbreviation. e.g. in 'tis).
'hinges' becomes 'i' (I can't justify this - if you can you should believe this answer much more).
'as'+'t'+'i'='ASTI'
'on' is the link.
Can you help me to learn more?
(Other definitions for asti that I've seen before include "White wine named after a town in Piedmont" , "It's a (anag) - wine" , "Bubbly wine" , "Italian drunk" , "Piedmont wine city, SE of Turin" .)