New idea put into Bond, leaving book, getting better (2,3,4)
I believe the answer is:
on the mend
'getting better' is the definition.
(on the mend means recovering from illness)
'new idea put into bond leaving book' is the wordplay.
I cannot really see how this works, but
'new' could be 'n' (common abbreviation eg NT for New Testament) and 'n' is located in the answer.
'idea' could be 'theme' (theme is a kind of idea) and 'theme' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for on the mend that I've seen before include "undergoing recovery?" , "returning to health" , "Improving in health" , "Becoming better in health" , "convalescing" .)