The most common and most likely answer to this crossword clue is the 8 letter word SNIPPIER
I've seen this crossword clue in Financial Times
S
N
I
P
P
I
E
R
Buddy explains!
The straight part
We know that "More critical" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case more critical = snippier.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 SNIPPIER mean?
SNIPPIER adjective- Fragmentary; snipped.
- Irritable; impatient; short-tempered.
- Stingy.