Note the new rent to put in the book (5)
I believe the answer is:
enter
'put in the book' is the definition.
'enter' can be an answer for 'book' (thesaurus). I am unsure of the 'put in the' bit.
'note the new rent' is the wordplay.
'note' becomes 'e' (musical note).
'the new' indicates anagramming the letters.
'rent' anagrammed gives 'nter'.
'e'+'nter'='ENTER'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for enter that I've seen before include "Come or go in" , "Go in and put in the ledger" , "submit?" , "Go in - set down" , "Enrol" .)