Book, full of anger, beginning to seem tedious (8)
I believe the answer is:
tiresome
'tedious' is the definition.
('tiresome' can be a synonym of 'tedious')
'book full of anger beginning to seem' is the wordplay.
'book' becomes 'tome' (tome is a kind of book**).
'full of' is an insertion indicator.
'anger' becomes 'ire' ('ire' can be a synonym of 'anger').
'beginning to' indicates taking the first letters.
The initial letter of 'seem' is 's'.
'ire'+'s'='ires'
'tome' placed around 'ires' is 'TIRESOME'.
(Other definitions for tiresome that I've seen before include "Exasperating" , "Is remote, being boring" , "So metier may be boring (8)" , "Tedious, dull" , "Boring, annoying" .)