Cruets of liquid sugar (8)
I believe the answer is:
fructose
'sugar' is the definition.
(fructose is a kind of sugar)
'cruets of liquid' is the wordplay.
'liquid' is an anagram indicator.
'cruets'+'of'='cruetsof'
'cruetsof' with letters rearranged gives 'FRUCTOSE'.
(Other definitions for fructose that I've seen before include "A simple sugar, in honey for instance" , "It's sweet" , "Fruit-sugar" , "Kind of sugar" , "Sweetener" .)