Reptile snapped at gorilla (9)

I believe the answer is:

alligator

I'm a little stuck... Click here to teach me more about this clue!

'reptile' is the definition.
(alligator is a kind of reptile)

'snapped at gorilla' is the wordplay.
'at gorilla' anagrams to 'ALLIGATOR'.
Though, I'm unsure how this is indicated.

Can you help me to learn more?

(Other definitions for alligator that I've seen before include "Large aquatic reptile" , "What can go with pear" , "Amphibious reptile" , "From fearsome beast" , "Animal of the crocodile family" .)

I've seen this clue in the Sydney Morning Herald.

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