It's an insignificant sweet! (6)
I believe the answer is:
trifle
'sweet' is the definition.
(trifle is a kind of sweet)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for trifle that I've seen before include "Party dessert" , "that doesn't matter" , "Pudding - bagatelle" , "A little thing for the pudding" , "Touch" .)