The most common and most likely answer to this crossword clue is the 3 plus 7 letter word THE RAINBOW
T
H
E
R
A
I
N
B
O
W
More clues leading to the result THE RAINBOW
Buddy explains!
The straight part
We know that "Multi-generational novel" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case multi-generational novel = the rainbow.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.