The most common and most likely answer to this crossword clue is the 9 letter word VAPORISER
I've seen this crossword clue in Financial Times
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Buddy explains!
The straight part
We know that "electronic cigarette" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case electronic cigarette = vaporiser.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 VAPORISER mean?
VAPORISER noun- A device with a heating element, used to vaporize a liquid.
- A device with a heating element, used to vaporize a liquid solution with medicine. The produced vapor condensates into fine aerosols, forming a mist inside the device, to be inhaled by the patient for delivery of the medicine into the lungs.