The most common and most likely answer to this crossword clue is the 5 letter word BLURB
B
L
U
R
B
More clues leading to the result BLURB
- Cry about reviewer’s initial description of book
- Puff of black cloud’s above
- What’s written to promote obscure book?
- Obscure book? This description might help
- Promotional material for obscure book
- Obscure book — and what might sell it
- Cry over author’s last words on dustjacket
- Obscure British advertising material
- Promotional words blemish book
- Lack of clarity with British promotional material
Buddy explains!

The straight part
We know that "What’s written to promote" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case what’s written to promote = blurb.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 BLURB mean?
BLURB noun- A short description of a book, film, or other work, written and used for promotional purposes.
- To write or quote in a blurb.
- To supply with a blurb.