Quick, like a crocodile? (6)
I believe the answer is:
snappy
I believe this is a double definition.
'quick' is the first definition.
(snappy means very fast)
'like a crocodile?' is the second definition.
(a crocodile snaps with its jaws)
(Other definitions for snappy that I've seen before include "Quick and energetic" , "Short and sweet" , "(Make it) quick" , "bad tempered" , "Irritable - quick - fashionable" .)