The most common and most likely answer to this crossword clue is the 8 letter word FROTHING
I've seen this crossword clue in The Sunday Telegraph
F
R
O
T
H
I
N
G
More clues leading to the result FROTHING
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 = frothing.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 FROTHING mean?
FROTHING verb- To create froth in (a liquid).
- (of a liquid) To bubble.
- To spit, vent, or eject, as froth.
- (literally) To spew saliva as froth; (figuratively) to rage, vent one's anger.
- To cover with froth.
- The act of something that froths.