It's rotten when a religious scholar went in front (6)
I believe the answer is:
addled
'it's rotten' is the definition.
(I've seen this in another clue)
'a religious scholar went in front' is the wordplay.
'religious scholar' becomes 'DD' (abbreviation for Doctor of Divinity).
'went in front' becomes 'led' (I've seen this in another clue).
'a'+'dd'+'led'='ADDLED'
'when' is the link.
(Other definitions for addled that I've seen before include "(Of an egg) went bad" , "turned bad" , "Dad led (anag.)" , "Confused, mixed up like bad egg" , "Scatterbrained like bad egg" .)