The most common and most likely answer to this crossword clue is the 7 letter word CALCIUM
I've seen this crossword clue in The Daily Telegraph
C
A
L
C
I
U
M
Buddy explains!

The straight part
We know that "Element" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case element = calcium.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 CALCIUM mean?
CALCIUM noun- The chemical element (Symbol Ca), with an atomic number 20. It is a soft, silvery-white alkaline earth metal which occurs naturally as carbonate in limestone and as silicate in many rocks.
- An atom of this element.