Fellow in tie carrying book (10)
I believe the answer is:
stablemate
'fellow' is the definition.
(I've seen this before)
'in tie carrying book' is the wordplay.
'in' is an insertion indicator.
'tie' becomes 'stalemate' (stalemate is a kind of tie).
'carrying book' becomes 'b' (I can't justify this - if you can you should give a lot more credence to this answer).
'stalemate' placed around 'b' is 'STABLEMATE'.
Can you help me to learn more?
(Other definitions for stablemate that I've seen before include "colleague in same organization" , "person in same outfit" , "Partner" , "One from the same organisation or background" , "Nag" .)