Is that woman's book simple or sage? (4)
I believe the answer is:
herb
'sage?' is the definition.
(sage is a kind of herb)
'is that woman's book' is the wordplay.
'is that woman's' becomes 'her' (belonging to a woman).
'book' becomes 'b' (abbreviation for book).
'her'+'b'='HERB'
'simple or' is the link.
This may not be correct. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for herb that I've seen before include "Aromatic plant used in cookery" , "Simple" , "man's name" , "Type of plant used in medicine" , "plant with useful properties" .)