Cat that weighs very little (5)
I believe the answer is:
ounce
I believe this clue is a double definition.
'cat' is the first definition.
(ounce can mean a snow leopard)
'that weighs very little' is the second definition.
(unit of weight)
(Other definitions for ounce that I've seen before include "Enough to tip the scales" , "prowler" , "Light weight coming in on cue" , "A light weight - feline" , "Jaguar" .)