Cat that will jump on the piano (5)
I believe the answer is:
ounce
'cat' is the definition.
(ounce can mean a snow leopard)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for ounce that I've seen before include "On cue (anag.)" , "scrap" , "Unit equal to about 28 grams" , "A light imperial measure of weight" , "Small imperial weight" .)