The most common and most likely answer to this crossword clue is the 4 plus 2 plus 3 plus 3 plus 3 letter word BANK OF MUM AND DAD
I've seen this crossword clue in Financial Times
B
A
N
K
O
F
M
U
M
A
N
D
D
A
D
Buddy explains!
The straight part
We know that "this" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case this = bank of mum and dad.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.