Irritate an insect (3)
I believe the answer is:
bug
I believe this clue is a double definition.
'irritate' is the first definition.
(I know that bug is a more specific form of the action bedevil)
'an insect' is the second definition.
(I know that insect can be written as bug)
(Other definitions for bug that I've seen before include "Computer glitch" , "Irritate" , "stripped down motor" , "Disease-germ" , "An enthusiast" .)