Several new among reds, say, with sulphur and appealing quality (11)
I believe the answer is:
winsomeness
'appealing quality' is the definition.
(I've seen this before)
'several new among reds say with' is the wordplay.
'several' becomes 'some' (similar in meaning).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'among' is an insertion indicator.
'reds' becomes 'wines' (wine is a kind of red).
'say with' becomes 's' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'some'+'n'='somen'
'somen' put inside 'wines' is 'winsomenes'.
'winsomenes'+'s'='WINSOMENESS'
'sulphur and' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
(Another definition for winsomeness that I've seen is " Appealing quality".)