Charge in circles (NOT into Crush) so his rockets can't get you. Wait until you hear a metal clinking noise and when you see a rocket lying on the floor, quickly go over to it and Spyro will pick it up. Then use A button (I think-haven't been on it for ages) to fire the rocket into Crush. Do this 3 times and he will die.

to defeat crush run from the ice things he throws untill it drops then get it then when
hes close to you throw it at him then charge at him