The most common and most likely answer to this crossword clue is the 8 letter word CATHODES
I've seen this crossword clue in The Times
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The straight part
We know that "Poles" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case poles = cathodes.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 CATHODES mean?
CATHODES noun- An electrode, of a cell or other electrically polarized device, through which a positive current of electricity flows outwards (and thus, electrons flow inwards). It usually, but not always, has a positive voltage.
- (by extension) The electrode at which chemical reduction of cations takes place, usually resulting in the deposition of metal onto the electrode.
- The electrode from which electrons are emitted into a vacuum tube or gas-filled tube.
- That electrode of a semiconductor device which is connected to the n-type material of a p-n junction.