Sweet little thing (6)
I believe the answer is:
trifle
This clue is a double definition.
'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 "Insignificant matter" , "Party dessert" , "Sweet - little thing" , "Small amount; dish" , "that doesn't matter" .)