The most common and most likely answer to this crossword clue is the 6 letter word CHROMA
I've seen this crossword clue in The Guardian
C
H
R
O
M
A
Buddy explains!
The straight part
We know that "quality of shade" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case quality of shade = chroma.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 CHROMA mean?
CHROMA noun- The colorfulness relative to the brightness of a similarly illuminated area
- The aspect of a colour's hue that depends on the amount of white or black in it; saturation
- A note in a chromatic scale