The most common and most likely answer to this crossword clue is the 9 letter word STEEPENED
I've seen this crossword clue in The Guardian
S
T
E
E
P
E
N
E
D
Buddy explains!
The straight part
We know that "rose sharply /rose sharply" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case rose sharply /rose sharply = steepened.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 STEEPENED mean?
STEEPENED verb- To make steeper.
- To become steeper.