You are not performing any removal in your code, you just instantiate an animation which plays automatically (I assume.)
You could destroy/disable your explosion after the animation has played. To achieve this, You could use a Coroutine to do this (wait inside the coroutine, then destroy/disable after a delay.) You could also use invoke.
Another way to do this would be to use Unity’s animation state machine system (Mecanim) and then just change state when the animation is over.
And I think you could also use animation events to call a function when the last frame has played.