The most common and most likely answer to this crossword clue is the 5 letter word GASSY
I've seen this crossword clue in The Daily Telegraph
G
A
S
S
Y
Buddy explains!
The straight part
We know that "Bubbly" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bubbly = gassy.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 GASSY mean?
GASSY adjective- Having the nature of, or containing, gas.
- Of food or drink: tending to cause flatulence.
- Tending to be long-winded or wordy, especially in a boastful and vain manner.