How do you use clock resonator in yu-gi-oh?

Answer 1

Clock Resonator has a continuous effect that will protect it from destruction by battle or by a card effect, once per turn, as long as it remains in face-up defence position.

So if it is in face-up defence position, and the opponent uses a destruction spell on it, or attacks it with a stronger monster, then once per turn you can allow it to survive. However since it's once per turn, if the opponent did both of them to it, then it would be destroyed by the second one.