The most common and most likely answer to this crossword clue is the 8 letter word CRITICAL
C
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T
I
C
A
L
More clues leading to the result CRITICAL
- Seriously ill judge starts to alarm
- Important law abruptly overturned by judge
- Major‘s really sick
- Finding fault is vital
- Finding faults serious
- Finding fault may be crucial
- Censorious to a dangerous degree?
- Wild Arctic tours I left, showing disapproval
- Fault-finding like one in an armchair perhaps
- Uncomplimentary reviewer, a student
Buddy explains!

The straight part
We know that "Major/really sick" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case major/really sick = critical.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 CRITICAL mean?
CRITICAL noun- A critical value, factor, etc.
- In breakdancing, a kind of airflare move in which the dancer hops from one hand to the other.
- Inclined to find fault or criticize
- Pertaining to, or indicating, a crisis or turning point.
- Extremely important.
- Relating to criticism or careful analysis, such as literary or film criticism.
- Of a patient condition involving unstable vital signs and a prognosis that predicts the condition could worsen; or, a patient condition that requires urgent treatment in an intensive care or critical care medical facility.
- Likely to go out of control if disturbed, that is, opposite of stable.
- Of the point (in temperature, reagent concentration etc.) where a nuclear or chemical reaction becomes self-sustaining.
- (physics) Of a temperature that is equal to the temperature of the critical point of a substance, i.e. the temperature above which the substance cannot be liquefied.