The most common and most likely answer to this crossword clue is the 4 letter word SLID
S
L
I
D
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The straight part
We know that "plummeted" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case plummeted = slid.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 SLID mean?
SLID verb- To (cause to) move in continuous contact with a surface
- To move on a low-friction surface.
- To drop down and skid into a base.
- To lose one’s balance on a slippery surface.
- To pass or put imperceptibly; to slip.
- To pass inadvertently.
- To pass along smoothly or unobservedly; to move gently onward without friction or hindrance.
- To pass from one note to another with no perceptible cessation of sound.