Very light cat? (5)
I believe the answer is:
ounce
I believe this clue is a double definition.
'very light' is the first definition.
(ounce is a very light unit of weight)
'cat?' is the second definition.
(ounce is a kind of cat)
(Other definitions for ounce that I've seen before include "Panther, perhaps" , "weight? Surely not" , "16 for a pound" , "Small imperial weight" , "One-sixteenth of pound" .)