The most common and most likely answer to this crossword clue is the 3 letter word YUS
Y
U
S
Buddy explains!

The straight part
We know that "jades" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case jades = yus.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 YUS mean?
YUS adverb- Alternative form of yes.
- Either of two letters, little yus (Ѧ) and big yus (Ѫ), representing nasal vowel sounds in the Cyrillic alphabet. The only major Slavic language retaining these sounds is Polish, which is written in the Latin alphabet.
- The letter Ю, ю.