The most common and most likely answer to this crossword clue is the 7 plus 2 plus 5 letter word QUARTER TO EIGHT
I've seen this crossword clue in The Daily Telegraph
Q
U
A
R
T
E
R
T
O
E
I
G
H
T
Buddy explains!
The straight part
We know that "1945" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case 1945 = quarter to eight.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.