Selection of wine: the Riesling's inferior (6)
I believe the answer is:
nether
'inferior' is the definition.
(thesaurus)
'selection of wine the riesling's' is the wordplay.
'selection of' says the answer is hidden in the clue.
'NETHER' is hidden in the letters of 'wine the rieslings'.
(Other definitions for nether that I've seen before include "inferior" , "Lower; Dutch '-lands'" , "These garments are for the bottom half" , "Lower in position" , "Located below" .)