oblivion ring

[clavio]

I play oblivion ring
opponent lets it resolve
I target seal of removal
He wants to destroy my top w/seal in response
Is this legal?

[Lifeless]

Yes. O-ring's ability goes on the stack when it comes in to play, and he gets a chance to respond. Assuming you meant Seal of Cleansing or "top" is an acronym for a creature name.

[Forbiddian]

The result is that your top is returned to your hand, and then Oring's ability is countered on resolution due to lack of a legal target, unless you have some other effect.

In response, though, you could put Sensei's Divining Top on top of your library (if you meant Seal of Cleansing).