The most common and most likely answer to this crossword clue is the 11 letter word CROCODILIAN
I've seen this crossword clue in The Times
C
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The straight part
We know that "snapper" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case snapper = crocodilian.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 CROCODILIAN mean?
CROCODILIAN noun- Any reptile of the order Crocodilia; a crocodile, alligator, caiman or gavial.