The most common and most likely answer to this crossword clue is the 4 plus 4 letter word NOSE DIVE
I've seen this crossword clue in The Times
N
O
S
E
D
I
V
E
More clues leading to the result NOSE DIVE
- Reportedly is familiar with disreputable bar — it will get you down fast!
- Dramatic decline in air travel?
- By sound of it, is aware of seedy club – sudden fall results?
- Dramatic drop in bill at seedy bar
- Not quite the last of the dwarfs? Frost perhaps arrested sharp decline
- A sudden drop, so I need changes involving volts
Buddy explains!
The straight part
We know that "it will get you down fast!" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case it will get you down fast! = nose dive.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.