The most common and most likely answer to this crossword clue is the 7 plus 3 letter word SALEM’S LOT
S
A
L
E
M
â
€
™
S
L
O
T
Buddy explains!
The straight part
We know that "Horror novel" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case horror novel = salem’s lot.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.