The most common and most likely answer to this crossword clue is the 4 letter word WAND
I've seen this crossword clue in The Times
W
A
N
D
More clues leading to the result WAND
Buddy explains!

The straight part
We know that "magic accessory" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case magic accessory = wand.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 WAND mean?
WAND noun- A hand-held narrow rod, usually used for pointing or instructing, or as a traditional emblem of authority.
- (by extension) An instrument shaped like a wand, such as a curling wand.
- A magic wand.
- A stick, branch, or stalk, especially of willow.
- A card of a particular suit of the minor arcana in tarot, the wands.
- To scan (e.g. a passenger at an airport) with a metal detector.