Stop a worm with a hand (3)
I believe the answer is:
paw
'a hand' is the definition.
(I know that hand can be written as paw)
'stop a worm with' is the wordplay.
'with' indicates the answer is hidden within the clue.
'PAW' is hidden in the letters of 'stop a worm'.
(Other definitions for paw that I've seen before include "Cat's foot" , "Mammal's foot" , "Hand; foot" , "Animal's foot" , "Animal foot or hill-billy dad" .)