Believer reformed lag in prison (8)
I believe the answer is:
anglican
'believer' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'reformed lag in prison' is the wordplay.
'reformed' is an anagram indicator.
'prison' becomes 'can' (the can is American slang for prison).
'lag'+'in'='lagin'
'lagin' is an anagram of 'angli'.
'angli'+'can'='ANGLICAN'
Can you help me to learn more?
(Other definitions for anglican that I've seen before include "As believer" , "Within the Church of England's communion" , "Religious person" , "Relating to the C of E or similar church" , "Belonging to the Church of England" .)