Debauchery for a number of years by new church (9)
I believe the answer is:
decadence
'debauchery' is the definition.
(I've seen this in another clue)
'number of years by new church' is the wordplay.
'number of years' becomes 'decade' (I've seen this before).
'by' is a charade indicator (letters next to each other).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'church' becomes 'ce' (abbreviation for Church of England).
'decade'+'n'+'ce'='DECADENCE'
'for a' is the link.
(Other definitions for decadence that I've seen before include "depravity" , "Decline in quality" , "Corruption" , "Debauchery, degeneracy" , "Progressive decline" .)