The most common and most likely answer to this crossword clue is the 3 plus 3 plus 2 plus 5 letter word RED SKY AT NIGHT
R
E
D
S
K
Y
A
T
N
I
G
H
T
More clues leading to the result RED SKY AT NIGHT
Buddy explains!
The straight part
We know that "prospect of a fine day" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case prospect of a fine day = red sky at night.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.