Former islander in church - only see improvement (9)
I believe the answer is:
ceylonese
'former islander in' is the definition.
Although both the answer and definition are adjectives, I don't see how they can define each other.
'church only see improvement' is the wordplay.
I cannot quite see how this works, but
'church' could be 'ce' (abbreviation for Church of England) and 'ce' is found in the answer.
an anagram of 'only' is 'ylon' which is located in the answer.
an anagram of 'see' is 'ese' which is present in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for ceylonese that I've seen is " Old islander".)