In southern Crete, perhaps, is there such service? (6)
I believe the answer is:
secret
'there such service?' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
'in southern crete perhaps' is the wordplay.
'in southern' becomes 's' (abbreviation. I am not sure about the 'in' bit.).
'perhaps' indicates anagramming the letters.
'crete' anagrammed gives 'ecret'.
's'+'ecret'='SECRET'
'is' is the link.
Can you help me to learn more?
(Other definitions for secret that I've seen before include "Confidential (information)" , "avoiding exposure" , "Not public" , "Confidential or mysterious" , "Not to be disclosed" .)