The most common and most likely answer to this crossword clue is the 8 letter word SEVERELY
I've seen this crossword clue in The Times
S
E
V
E
R
E
L
Y
More clues leading to the result SEVERELY
- Seriously cut off location in fens
- Extremely cut off cathedral city
- Very badly cut, see?
- Very much cut off, see
- Look at bank’s investing very critically
- Cut by the Spanish youngster originally in a very plain style
- In drastic way, cut off cathedral city
- Critically cut off cathedral city
- Unsympathetically terminate/end love with heartless lady
Buddy explains!

The straight part
We know that "Extremely" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case extremely = severely.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 SEVERELY mean?
SEVERELY adverb- In a severe manner.