It’s a set-up offering white wine (4)
I believe the answer is:
asti
'white wine' is the definition.
(I've seen this before)
'it's a set-up' is the wordplay.
'set up' is a reversal indicator.
'its'+'a'='itsa'
'itsa' back-to-front is 'ASTI'.
'offering' is the link.
(Other definitions for asti that I've seen before include "Piedmont wine city, SE of Turin" , "Sparkling wine named after an Italian Piedmont town" , "Italian town, famous for its wine" , "White wine named after a town in Piedmont" , "Bubbly wine" .)