The most common and most likely answer to this crossword clue is the 9 letter word KEYSTONES
I've seen this crossword clue in The Daily Telegraph
K
E
Y
S
T
O
N
E
S
More clues leading to the result KEYSTONES
Buddy explains!
The straight part
We know that "necessary elements of support" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case necessary elements of support = keystones.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 KEYSTONES mean?
KEYSTONES noun- The top stone of an arch.
- Something on which other things depend for support.
- A native or resident of the American state of Pennsylvania.
- (retail) A retail price that is double the cost price; a markup of 100%.
- The combination of the shortstop and second baseman.