The most common and most likely answer to this crossword clue is the 10 letter word DILIGENTLY
I've seen this crossword clue in The Sunday Telegraph
D
I
L
I
G
E
N
T
L
Y
Buddy explains!

The straight part
We know that "with care" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case with care = diligently.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 DILIGENTLY mean?
DILIGENTLY adverb- In a diligent manner, with appropriate effort, carefully.