Bag with tea contained and sweetener (9)
I believe the answer is:
saccharin
'sweetener' is the definition.
(I know that saccharin is a type of sweetener)
'bag with tea contained' is the wordplay.
'bag' becomes 'sac' (a small bag).
'with' says to put letters next to each other.
'tea' becomes 'char' (I've seen this before).
'contained' becomes 'in' (I can't justify this - if you can you should give a lot more credence to this answer).
'sac'+'char'+'in'='SACCHARIN'
'and' is the link.
Can you help me to learn more?
(Other definitions for saccharin that I've seen before include "Calorie-free sweetener" , "alternative sweetener" , "Very sweet compound" , "sweetener provided" , "Sweet substance used as sugar substitute" .)