The most common and most likely answer to this crossword clue is the 3 plus 5 plus 5 letter word THE NOBEL GASES
T
H
E
N
O
B
E
L
G
A
S
E
S
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.