Book is on what make us who we are (7)
I believe the answer is:
genesis
'book' is the definition.
(first book of the Bible)
'is on what make us who we are' is the wordplay.
'on' is a charade indicator (letters next to each other).
'what make us who we are' becomes 'genes' (DNA).
'is' put after 'genes' is 'GENESIS'.
(Other definitions for genesis that I've seen before include "Origin -- see sign (anag)" , "rock band" , "rock group" , "Band; book" , "Old Testament Book 1" .)