The most common and most likely answer to this crossword clue is the 7 letter word STAPLES
S
T
A
P
L
E
S
Buddy explains!

The straight part
We know that "Key elements" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case key elements = staples.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 STAPLES mean?
STAPLES noun- A town containing merchants who have exclusive right, under royal authority, to purchase or produce certain goods for export; also, the body of such merchants seen as a group.
- (by extension) Place of supply; source.
- The principal commodity produced in a town or region.
- A basic or essential supply.
- A recurring topic or character.
- Short fiber, as of cotton, sheep’s wool, or the like, which can be spun into yarn or thread.
- Unmanufactured material; raw material.
- To sort according to its staple.
- A wire fastener used to secure stacks of paper by penetrating all the sheets and curling around.
- A wire fastener used to secure something else by penetrating and curling.
- A U-shaped metal fastener, used to attach fence wire or other material to posts or structures.
- One of a set of U-shaped metal rods hammered into a structure, such as a piling or wharf, which serve as a ladder.
- A shaft, smaller and shorter than the principal one, joining different levels.
- A small pit.
- A district granted to an abbey.
- A post; prop; support
- To secure with a staple.