Island in Asia perhaps in which a doctor turns up (8)
I believe the answer is:
sardinia
'island' is the definition.
(Sardinia is an example)
'in asia perhaps in which a doctor turns up' is the wordplay.
'perhaps' indicates an anagram.
'in which' means one lot of letters goes inside another.
'a doctor' becomes 'dr' (abbreviation).
'turns up' says the letters should be written in reverse.
'dr' back-to-front is 'rd'.
'in'+'asia'='inasia'
'inasia' with letters rearranged gives 'sainia'.
'sainia' enclosing 'rd' is 'SARDINIA'.
(Other definitions for sardinia that I've seen before include "Corsican neighbour" , "Second-largest Mediterranean island, after Sicily" , "Island south of Corsica" , "Adrian is seen in Mediterranean island" , "Large Italian island, capital Cagliari" .)