A sweet little thing (6)
I believe the answer is:
trifle
I believe this clue is a double definition.
'a sweet' is the first definition.
(trifle is a kind of sweet)
'little thing' is the second definition.
(trifle can mean something trivial or insignificant)
(Other definitions for trifle that I've seen before include "Party dessert" , "Triviality" , "Insignificant item - dessert" , "Dessert - something unimportant" , "Touch" .)