Pound fraction (5)
I believe the answer is:
ounce
'pound fraction' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for ounce that I've seen before include "16 for a pound" , "Carnivore" , "Unit equal to about 28 grams" , "little weight" , "Unit of weight - snow leopard" .)