Is she an option? (4)
I believe the answer is:
else
'is she' is the definition.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for else that I've seen before include "Besides, otherwise" , "In addition, besides" , "Other than (what is under consideration)" , "Adverb meaning if not, otherwise" , "Besides; instead" .)