The most common and most likely answer to this crossword clue is the 6 letter word EFFACE
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More clues leading to the result EFFACE
Buddy explains!

The straight part
We know that "Obliterate" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case obliterate = efface.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does EFFACE mean?
EFFACE verb- To erase (as anything impressed or inscribed upon a surface); to render illegible or indiscernible.
- To cause to disappear as if by rubbing out or striking out.
- To make oneself inobtrusive as if due to modesty or diffidence.
- Of the cervix during pregnancy, to thin and stretch in preparation for labor.