Greek islander hiding in secret annexe (6)
I believe the answer is:
cretan
'greek islander' is the definition.
(I've seen this in another clue)
'hiding in secret annexe' is the wordplay.
'hiding' says the answer is hidden in the clue.
'CRETAN' is hidden in the letters of 'in secret annexe'.
(Other definitions for cretan that I've seen before include "From Greece" , "Native of Minoan island" , "Island nationality of citizen of Heraklion" , "Greek islander" , "A Mediterranean islander" .)