Branch of society unfavourable about Knight - here’s the evidence (7,3,5)
I believe the answer is:
chapter and verse
'here's the evidence' is the definition.
(a reference or proof for a claim)
'branch of society unfavourable about knight' is the wordplay.
'branch of society' becomes 'chapter'.
'unfavourable' becomes 'adverse' (similar in meaning).
'about' means one lot of letters goes inside another.
'knight' becomes 'n' (chess).
'adverse' going around 'n' is 'andverse'.
'chapter'+'andverse'='CHAPTER AND VERSE'
(Other definitions for chapter and verse that I've seen before include "location of Biblical text" , "precise testimony" , "complete specification" , "Full" , "in detail" .)