Swamp snapper (4)
I believe the answer is:
croc
'swamp snapper' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for croc that I've seen before include "Small reptile" , "Large, bony-plated reptile (abbr)" , "Wild animal" , "Single-handed mariner's nemesis" , "that might be sitting on your foot" .)