The most common and most likely answer to this crossword clue is the 5 plus 5 letter word SPRAY PAINT
I've seen this crossword clue in The Times
S
P
R
A
Y
P
A
I
N
T
More clues leading to the result SPRAY PAINT
Buddy explains!
The straight part
We know that "decoration to be sent by jet" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case decoration to be sent by jet = spray paint.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.