Tough person defending book (8)
I believe the answer is:
hardback
'defending book' is the definition.
'hardback' can be an answer for 'book' (hardback is a kind of book). I'm unsure of the 'defending' bit.
'tough person' is the wordplay.
'tough' becomes 'hard' (similar in meaning).
'person' becomes 'back' (back is a kind of person).
'hard'+'back'='HARDBACK'
Can you help me to learn more?
(Other definitions for hardback that I've seen before include "Penguins are rarely so" , "Style of book binding" , "Sort of book" , "Durable version of book" , "Book with stiff covers" .)