The most common and most likely answer to this crossword clue is the 4 plus 6 letter word PAGE TURNER
I've seen this crossword clue in Financial Times
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More clues leading to the result PAGE TURNER
Buddy explains!
The straight part
We know that "The Musician’s Assistant/a thrilling novel" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the musician’s assistant/a thrilling novel = page turner.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 PAGE TURNER mean?
PAGE TURNER noun- A written work, usually a novel, which is sufficiently interesting or suspenseful to keep the reader 'turning the pages'.