Cryptic crossword clue
Powerless to protect deposit? Extremely interesting 13

The most common and most likely answer to this crossword clue is the 13 letter word UNPUTDOWNABLE

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Buddy explains!

The straight part
We know that "Extremely interesting" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case extremely interesting = unputdownable.
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 UNPUTDOWNABLE mean?

UNPUTDOWNABLE adjective
  1. Of a person, etc.: difficult or impossible to put down (in various senses).
  2. (specifically) Of a book or other written work: so captivating or engrossing that one cannot bear to stop reading it.

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