Performs patch test regularly (4)
I believe the answer is:
acts
'performs' is the definition.
(acting is a kind of performing)
'patch test regularly' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'patch'+'test'='patchtest'
The alternate letters of 'patchtest' are 'ACTS'.
(Other definitions for acts that I've seen before include "Theatrical deeds" , "Things done" , "Religious book" , "NT book; laws" , "Goes" .)