Small venomous snakes (4)
I believe the answer is:
asps
'small venomous snakes' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for asps that I've seen before include "Poplars" , "poisonous things" , "Cleopatra's cobras" , "Egyptian cobras" , "Deadly snakes" .)