It's cold tea at home with sweetener (9)
I believe the answer is:
saccharin
'sweetener' is the definition.
(saccharin is a kind of sweetener)
'it's cold tea at home' is the wordplay.
'it' becomes 'sa' (old-fashioned abbreviation for sex appeal).
'cold' becomes 'c' (eg on taps).
'tea' becomes 'char' (I've seen this before).
'at home' becomes 'in' ('in' can be similar in meaning to 'at home').
'sa'+'c'+'char'+'in'='SACCHARIN'
'with' is the link.
(Other definitions for saccharin that I've seen before include "Very sweet compound" , "Artificial sweetener" , "Calorie-free sweetener" , "sweetener provided" , "Synthetic sweetener" .)