The most common and most likely answer to this crossword clue is the 8 letter word SAGITTAL
S
A
G
I
T
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A
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The straight part
We know that "like a missile" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case like a missile = sagittal.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 SAGITTAL mean?
SAGITTAL adjective- In the direction from dorsal to ventral.
- Of or relating to an arrow; resembling an arrow; furnished with an arrow-like appendage.