Retreat that is concealing means of identification to the east of small island (9)
I believe the answer is:
hermitage
'retreat' is the definition.
(I've seen this before)
'that is concealing means of identification to the east of small island' is the wordplay.
'that is' becomes 'ie' ('i.e.' can be a synonym of 'that is').
'concealing' indicates putting letters inside.
'means of identification' becomes 'tag'.
'to the east of' is a charade indicator (letters next to each other).
'small island' becomes 'herm' (Channel Island).
'ie' enclosing 'tag' is 'itage'.
'itage' put after 'herm' is 'HERMITAGE'.
(Other definitions for hermitage that I've seen before include "Home of a recluse" , "accommodation for one" , "Secluded retreat" , "Place of retreat" , "art museum" .)