Red or white wine: red is odd, initially, certainly from Riesling grower? (5)
I believe the answer is:
rioja
'red' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for rioja that I've seen before include "Open space (ancient Greek)" , "Spanish wine type" , "Spanish drink" , "it comes from grapevine" , "Dry red wine from Spain" .)