The most common and most likely answer to this crossword clue is the 8 letter word LIKENING
I've seen this crossword clue in The Guardian
L
I
K
E
N
I
N
G
Buddy explains!
The straight part
We know that "Comparing" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case comparing = likening.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 LIKENING mean?
LIKENING verb- (followed by to or unto) To compare; to state that (something) is like (something else).
- The act by which things are likened; a comparison.