Weight of a big cat (5)
I believe the answer is:
ounce
This clue is a double definition.
'weight' is the first definition.
(I know that ounce is a type of troy unit)
'a big cat' is the second definition.
(I know that ounce is a type of big cat)
'of' is the link.
(Other definitions for ounce that I've seen before include "16 for a pound" , "There are quite a few in the pound" , "Unit of weight - snow leopard" , "Lightweight" , "Wild cat - small weight" .)