Church on island visited by a very loud bird (9)
I believe the answer is:
Here is my best explanation:
'bird' is the definition.
(chaffinch is a kind of bird)
'church on island visited by a very loud' is the subsidiary indication.
'church' becomes 'ch' (common abbreviation).
'on' means one lot of letters go next to another.
'island' becomes 'inch' (**).
'visited by' means one lot of letters goes inside another.
'very loud' becomes 'ff'.
'chinch' enclosing 'aff' is 'chaffinch'.
(Other definitions for chaffinch that I've seen before include "Garden bird", "European bird with black and white wings", "Common bird" and "Small European songbird".)