The most common and most likely answer to this crossword clue is the 8 letter word BLOWFISH
I've seen this crossword clue in The Times
B
L
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F
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H
Buddy explains!
The straight part
We know that "puffer" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case puffer = blowfish.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 BLOWFISH mean?
BLOWFISH noun- Any species of fish of the family Tetraodontidae that have the ability to inflate themselves to a globe several times their normal size by swallowing water or air when threatened.
- A delicacy popular in Japan, consisting of the fish served raw as sushi or perhaps fried. It may, if improperly prepared, contain considerably deadly levels of neurotoxins.