The most common and most likely answer to this crossword clue is the 9 letter word BLATHERED
I've seen this crossword clue in The Guardian
B
L
A
T
H
E
R
E
D
Buddy explains!
The straight part
We know that "was full of hot air/was full of hot air" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case was full of hot air/was full of hot air = blathered.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 BLATHERED mean?
BLATHERED verb- To talk rapidly without making much sense.
- To say (something foolish or nonsensical); to say (something) in a foolish or overly verbose way.