Patch test regularly revealing performances (4)
I believe the answer is:
acts
'performances' is the definition.
(act is a kind of performance)
'patch test regularly' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'patch'+'test'='patchtest'
The alternating letters of 'patchtest' are 'ACTS'.
'revealing' is the link.
(Other definitions for acts that I've seen before include "Theatrical deeds" , "Follower of John" , "Dramatic parts" , "performers for revue, say?" , "Parliaments pass them" .)