The most common and most likely answer to this crossword clue is the 5 plus 4 letter word GIANT STAR
I've seen this crossword clue in Financial Times
G
I
A
N
T
S
T
A
R
More clues leading to the result GIANT STAR
Buddy explains!

The straight part
We know that "Mira may be" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mira may be = giant star.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.