The most common and most likely answer to this crossword clue is the 9 letter word PLANELOAD
I've seen this crossword clue in Financial Times
P
L
A
N
E
L
O
A
D
Buddy explains!

The straight part
We know that "A crate-full" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a crate-full = planeload.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.
What does PLANELOAD mean?
PLANELOAD noun- As much, or as many, as a plane can carry