It's annoying that anger's a part of great book (8)
I believe the answer is:
tiresome
'it's annoying' is the definition.
(I've seen this before)
'anger's a part of great book' is the wordplay.
'anger's' becomes 'ire's' (ire is intense rage).
'a part of' indicates putting letters inside (part of the inside).
'great book' becomes 'tome' (a tome is a large book).
'ires' put inside 'tome' is 'TIRESOME'.
'that' acts as a link.
(Other definitions for tiresome that I've seen before include "Causing impatience" , "So metier may be boring (8)" , "Exasperating" , "Tedious and boring" , "Boring, annoying" .)