Island in conservation area (4)
I believe the answer is:
iona
'island' is the definition.
(I've seen this before)
'in conservation area' is the wordplay.
'in' says the answer is hidden in the clue.
'IONA' can be found hidden inside 'conservation area'.
(Other definitions for iona that I've seen before include "Saint Columba's isle" , "St Columba's monastery isle" , "Scots monastery isle" , "Scottish island from where Christianity spread in 563 AD" , "place in the Hebrides" .)