Chief is regularly stroppy (3)
I believe the answer is:
top
'chief' is the definition.
('top' can be a synonym of 'chief')
'regularly stroppy' is the wordplay.
'regularly' indicates alternate letters (regularly take one letter, leave next etc.).
The alternating letters of 'stroppy' are 'TOP'.
'is' is the link.
(Other definitions for top that I've seen before include "Highest, child's toy" , "Kill" , "Apex; child's toy" , "Best" , "Pinnacle" .)