The most common and most likely answer to this crossword clue is the 6 letter word COOMBE
C
O
O
M
B
E
Buddy explains!

The straight part
We know that "Deep (but short) depression" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case deep (but short) depression = coombe.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 COOMBE mean?
COOMBE noun- A valley, often wooded and often with no river
- A cirque.