Territory taken back in Egyptianisation (5)
I believe the answer is:
sinai
'territory' is the definition.
(the Sinai Peninsula is an area in Egypt)
'taken back in egyptianisation' is the wordplay.
'taken back' shows that the letters should be reversed in order.
'in' says the answer is hidden in the clue.
'ianis' is hidden in the letters of 'egyptianisation'.
'ianis' written backwards gives 'SINAI'.
(Other definitions for sinai that I've seen before include "Mt. where Moses received 10 Commandments" , "Mount on which Moses received the Ten Commandments" , "Mount where Moses received God's law" , "Mountainous peninsula in Egypt" , "Mountain in Egypt" .)