The most common and most likely answer to this crossword clue is the 5 letter word BEGIN
I've seen this crossword clue in The Guardian
B
E
G
I
N
More clues leading to the result BEGIN
Buddy explains!

The straight part
We know that "Dawn/Dawn" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dawn/dawn = begin.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 BEGIN mean?
BEGIN noun- Beginning; start.
- To start, to initiate or take the first step into something.
- To be in the first stage of some situation
- To come into existence.