Pharaohs in Aida retaining Egyptian land (5)
I believe the answer is:
sinai
'egyptian land' is the definition.
'pharaohs in aida retaining' is the wordplay.
'retaining' says the answer is hidden in the clue.
'SINAI' can be found hidden inside 'pharaohs in aida'.
(Other definitions for sinai that I've seen before include "Mountain in Egypt" , "Mount where Moses received God's law" , "One showing genetic change" , "Mountainous peninsula in Egypt" , "Ten Commandments mountain" .)