The most common and most likely answer to this crossword clue is the 7 letter word TOMFOOL
I've seen this crossword clue in The Times
T
O
M
F
O
O
L
More clues leading to the result TOMFOOL
Buddy explains!

The straight part
We know that "Idiotic" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case idiotic = tomfool.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 TOMFOOL mean?
TOMFOOL noun- A silly or stupid person, especially a boy or man.
- Any of various tyrant flycatchers viewed as foolishly confiding.
- To act foolishly.
- Silly or stupid.