Mount climbed by Moses (5)
I believe the answer is:
'mount climbed by moses' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sinai that I've seen before include "Mt. where Moses received 10 Commandments" , "11 Across peninsula" , "Mountain in Egypt" , "Mountainous Egyptian peninsula" , "Egyptian location" .)