The most common and most likely answer to this crossword clue is the 8 letter word POLONIUM
P
O
L
O
N
I
U
M
More clues leading to the result POLONIUM
Buddy explains!

The straight part
We know that "a particular element" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case a particular element = polonium.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 POLONIUM mean?
POLONIUM noun- A rare, highly radioactive chemical element (symbol Po) with atomic number 84.