The most common and most likely answer to this crossword clue is the 10 letter word BLOCKHEADS
I've seen this crossword clue in The Daily Telegraph
B
L
O
C
K
H
E
A
D
S
More clues leading to the result BLOCKHEADS
Buddy explains!

The straight part
We know that "Idiots" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case idiots = blockheads.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 BLOCKHEADS mean?
BLOCKHEADS noun- A stupid person.
- A sideshow performer who hammers nails or similar items through his or her nostril into the nasal cavity; human blockhead.
- To perform as a human blockhead.
- To behave in a stupid manner.