The most common and most likely answer to this crossword clue is the 7 letter word SHOOTER
I've seen this crossword clue in Financial Times
S
H
O
O
T
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R
More clues leading to the result SHOOTER
Buddy explains!
The straight part
We know that "arm" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case arm = shooter.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 SHOOTER mean?
SHOOTER noun- Someone who shoots something; a gunner, archer etc.
- A firearm.
- A video game in which shooting enemies (or targets) is the main objective.
- A professional wrestler who uses actual fighting moves as part of his style, or who speaks his mind during a live or televised event (instead of speaking from a script).
- A large marble used for knocking smaller marbles out of a chalk circle.
- An alcoholic beverage typically served in a shot glass.
- A shooting star.
- A device supposed to accumulate orgone.