Mount where Moses received the Ten Commandments (5)
I believe the answer is:
sinai
'mount where moses received the ten commandments' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for sinai that I've seen before include "Mount on which Moses received the Ten Commandments" , "One showing genetic change" , "Mount where Moses received God's law" , "Biblical mount" , "Mt. where Moses received 10 Commandments" .)