Bad actors (4)
'bad actors' is the definition.
(as in a hammy actor)
This is all the clue.
(Other definitions for hams that I've seen before include "inept performers" , "Sit on such" , "Overacts (colloq.)" , "Poor actors" .)
(Other definitions for worms that I've seen before include "Early birds' diet" , "Burrowing invertebrates" , "harmful programs" , "Long soft-bodied limbless invertebrates" , "despicable people" .)