The most common and most likely answer to this crossword clue is the 2 letter word AS
A
S
More clues leading to the result AS
Buddy explains!

The straight part
We know that "Unaltered" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case unaltered = as.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 AS mean?
AS adverb- To such an extent or degree; to the same extent or degree.
- Considered to be, in relation to something else; in the relation (specified).
- For example; for instance. (Compare such as.)
- Introducing a basis of comparison, with an object in the objective case.
- In the role of.
- In the (same) way or manner that; to the (same) degree that.
- At the time that; during the time when:
- Being that, considering that, because, since.
- Introducing a comparison with a hypothetical state (+ subjunctive, or with the verb elided): as though, as if.
- Functioning as a relative conjunction, and sometimes like a relative pronoun: that, which, who. (See usage notes.)
- (possibly obsolete) Than.
- (unit of weight) A libra.
- Any of several coins of Rome, coined in bronze or later copper; or the equivalent value.