The most common and most likely answer to this crossword clue is the 8 letter word LEANNESS
I've seen this crossword clue in The Daily Telegraph
L
E
A
N
N
E
S
S
More clues leading to the result LEANNESS
Buddy explains!

The straight part
We know that "Possibly an anorexic quality" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case possibly an anorexic quality = leanness.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.