Quiet snow leopard to attack suddenly (6)
I believe the answer is:
pounce
'attack suddenly' is the definition.
(I've seen this in another clue)
'quiet snow leopard' is the wordplay.
'quiet' becomes 'p' (music symbol for 'piano', ie soft or quiet).
'snow leopard' becomes 'ounce' (ounce is an alternative name for the snow leopard).
'p'+'ounce'='POUNCE'
'to' is the link.
(Other definitions for pounce that I've seen before include "Strike" , "Spring upon suddenly" , "Suddenly spring; fine powder" , "(Of cat) sudden leap to seize prey" , "Spring (on prey like a cat)" .)