The most common and most likely answer to this crossword clue is the 11 letter word ELECTRICIAN
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More clues leading to the result ELECTRICIAN
Buddy explains!

The straight part
We know that "(someone) who could put your lights out (and charge you to fix them!)" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case (someone) who could put your lights out (and charge you to fix them!) = electrician.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 ELECTRICIAN mean?
ELECTRICIAN noun- A tradesman who installs, repairs and maintains electrical wiring and equipment.
- A scientist who studies electricity.