The most common and most likely answer to this crossword clue is the 3 plus 5 plus 7 letter word THE WHOLE SHEBANG
I've seen this crossword clue in Financial Times
T
H
E
W
H
O
L
E
S
H
E
B
A
N
G
More clues leading to the result THE WHOLE SHEBANG
Buddy explains!
The straight part
We know that "everything" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case everything = the whole shebang.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.