Doctor is in a part of Egypt (5)
I believe the answer is:
sinai
'part of egypt' is the definition.
('Sinai' is part of 'egypt')
'doctor is in a' is the wordplay.
'doctor' indicates anagramming the letters.
'is'+'in'+'a'='isina'
'isina' is an anagram of 'SINAI'.
(Other definitions for sinai that I've seen before include "Egyptian location" , "Peninsula, mostly desert, at north end of Red Sea" , "Ten Commandments mountain" , "Mount on which Moses received the Ten Commandments" , "Part of 10 [EGYPT]" .)