The most common and most likely answer to this crossword clue is the 10 letter word COMMUTATOR
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Buddy explains!
The straight part
We know that "Device for reversing current" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case device for reversing current = commutator.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 COMMUTATOR mean?
COMMUTATOR noun- An electrical switch, in a generator or motor, that periodically reverses the direction of an electric current.
- A binary map in a given group G, given by [g, h] = ghg−1h−1, where g and h are elements of G, which yields the group's identity if and only if the group operation commutes for g and h.
- A binary map in a given ring R, given by [a, b] = ab − ba, where a and b are elements of R, which yields the ring's zero element if and only if the multiplication operation commutes for a and b.