The most common and most likely answer to this crossword clue is the 6 letter word MORONS
I've seen this crossword clue in The Times
M
O
R
O
N
S
More clues leading to the result MORONS
Buddy explains!

The straight part
We know that "fools" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case fools = morons.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 MORONS mean?
MORONS noun- A stupid person; an idiot; a fool.
- A person of mild mental subnormality in the former classification of mental retardation, having an intelligence quotient of 50–70.