When to pen court decrees (4)
I believe the answer is:
acts
'decrees' is the definition.
(I've seen this before)
'when to pen court' is the wordplay.
'when' becomes 'as'.
'to pen' indicates putting letters inside.
'court' becomes 'ct'.
'as' enclosing 'ct' is 'ACTS'.
(Other definitions for acts that I've seen before include "Goes" , "Fifth book of the New Testament" , "straight after John" , "5th NT book" , "Dramatic parts" .)