Serpentine form (3)
I believe the answer is:
boa
'serpentine form' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for boa that I've seen before include "... cold-blooded creature" , "native American" , "Fluffy scarf of feathers" , "S American snake that crushes its prey" , "One covered in scales" .)