Regularly insult head (3)
I believe the answer is:
nut
'head' is the definition.
(informal term for somebody's head)
'regularly insult' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternate letters of 'insult' are 'NUT'.
(Other definitions for nut that I've seen before include "Freak" , "eccentric type" , "piece of coal" , "Fanatic (slang)" , "Enthusiastic person" .)