The most common and most likely answer to this crossword clue is the 13 letter word ESTABLISHMENT
I've seen this crossword clue in The Daily Telegraph
E
S
T
A
B
L
I
S
H
M
E
N
T
More clues leading to the result ESTABLISHMENT
- This bent male’s running the organisation
- Governing body that puts out NHS timetables
- Ablest men upset with this business
- People in battle hiss corrupted institution
- Extravagant man’s belt is the business
- Blithe man’s set to ruin business
- Firm foundation
- Basement’s hit in explosion burying large foundation
- Setting up English, try hard workers in roster
- Formation fighting his battles capturing soldiers
Buddy explains!

The straight part
We know that "foundation" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case foundation = establishment.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 ESTABLISHMENT mean?
ESTABLISHMENT noun- The act of establishing; a ratifying or ordaining; settlement; confirmation.
- The state of being established, founded, etc.; fixed state.
- That which is established; as a form of government, a permanent organization, business or force, or the place where one is permanently fixed for residence.
- (usually with "the") The ruling class or authority group in a society; especially, an entrenched authority dedicated to preserving the status quo. Also Establishment.
- The number of staff required to run a department or organisation (often used in the context of healthcare and other public services).