The most common and most likely answer to this crossword clue is the 9 letter word BRAINWAVE
B
R
A
I
N
W
A
V
E
More clues leading to the result BRAINWAVE
- Something inspired primarily by wet weather, with hail
- Boris just started on downfall – gesture “Great idea!”
- Inwardly, not half grabbed by courageous idea
- British party welcoming stylish women with a bright idea
- Bishop drops gesture? Good idea!
- Idea getting support with weight in one section of church
- A trendy wife included in bold idea
- Greeting by head giving sudden inspiration
- View a barn that’s renovated — it prompts fresh thinking?
- Analysing a win secured by gutsy inspiration
Buddy explains!

The straight part
We know that "Idea" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case idea = brainwave.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 BRAINWAVE mean?
BRAINWAVE noun- Any of many rhythmic fluctuations of electric potential between parts of the brain, especially those seen on an electroencephalogram
- A sudden idea, understanding, or inspiration; a brainstorm