Church know lady regularly betrayed husband (7)
I believe the answer is:
cuckold
'betrayed husband' is the definition.
(I've seen this before)
'church know lady regularly' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'church'+'know'+'lady'='churchknowlady'
The alternating letters of 'churchknowlady' are 'CUCKOLD'.
(Other definitions for cuckold that I've seen before include "Betrayed husband" , "fool of a husband" , "cheat on hubbies" , "Man with an unfaithful wife" , "Man whos wife is cheating on him?" .)