Made rare synthetic sugar (8)
I believe the answer is:
demerara
'sugar' is the definition.
(I've seen this before)
'made rare synthetic' is the wordplay.
'synthetic' is an anagram indicator.
'made'+'rare'='maderare'
'maderare' anagrammed gives 'DEMERARA'.
(Other definitions for demerara that I've seen before include "Light brown cane sugar" , "Variety of sugar" , "Rum" , "sugar - and alcohol" , "That's sweet!" .)