The most common and most likely answer to this crossword clue is the 9 letter word POTASSIUM
I've seen this crossword clue in Financial Times
P
O
T
A
S
S
I
U
M
More clues leading to the result POTASSIUM
- Wrong assumption, discounting knight — here’s a K
- An element of love, quiet reflecting, is a must, somehow
- ‘K‘ is wrestling with Pat
- Metal initially in back of truck, for example?
- Metal container a girl overturned outside community centre
- Smashing atoms up is to create element
- Metal toy with miao! Puss tempted at first
- Making a comeback, Emu is sat opposite, not completely in element?
- Revising the order, Sam is up to “K”
- Element of autism so upsetting after onset of paranoia
Buddy explains!

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 POTASSIUM mean?
POTASSIUM noun- A soft, waxy, silvery reactive metal that is never found unbound in nature; an element (symbol K) with an atomic number of 19 and atomic weight of 39.0983. The symbol is derived from the Latin kalium.
- A single atom of this element.