Unimportant thing (6)
I believe the answer is:
trifle
'unimportant thing' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for trifle that I've seen before include "Something of small importance" , "nothing?" , "Pudding - bagatelle" , "Knick-knack" , "Small amount; dessert" .)