The most common and most likely answer to this crossword clue is the 5 letter word NULLA
I've seen this crossword clue in Independent
N
U
L
L
A
More clues leading to the result NULLA
Buddy explains!
The straight part
We know that "ravine" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case ravine = nulla.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 NULLA mean?
NULLA noun- Alternative form of nulla-nulla
- A stream-bed, ravine, or other watercourse; a drain for rain or floodwater.