The most common and most likely answer to this crossword clue is the 8 letter word NEPHRITE
I've seen this crossword clue in The Guardian
N
E
P
H
R
I
T
E
More clues leading to the result NEPHRITE
Buddy explains!

The straight part
We know that "Jade" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case jade = nephrite.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 NEPHRITE mean?
NEPHRITE noun- A semi-precious stone, one of the two types of stone commonly referred to as jade (the other being jadeite).