The most common and most likely answer to this crossword clue is the 4 letter word NEIL
N
E
I
L
More clues leading to the result NEIL
- That’s number recalled first from Louis Armstrong?
- Man altered line
- Man right to be elevated
- Irishman‘s right to return
- Boy is right to keep up
- For starters, no earthling is lying — He took a giant step for mankind!
- Man showing love, having swallowed drug
- Armstrong beheaded alien, running the other way
- Mr. Diamond’s financial claim rejected
Buddy explains!

The straight part
We know that "Armstrong" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case armstrong = neil.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.