There is no such feature and it would probably overcomplicate things, as well as incentivize wrong behaviors (creating drafts just to "stake" being first to answer and so on).
If you feel your answer is incomplete it is perfectly fine to use your words and say so in the body of the answer.
If I am not confident I understand the question completely/correctly I will typically start answer with my understanding of it:
If I follow you right you want to accomplish X under Y circumstances.
This may be a good starting point in such case...
