Peacekeepers love stopping hatred, it's agreed (9)
I believe the answer is:
unanimous
'agreed' is the definition.
(thesaurus)
'peacekeepers love stopping hatred' is the wordplay.
'peacekeepers' becomes 'un'.
'love' becomes 'o' (In tennis, 'love' means 'zero').
'stopping' is an insertion indicator (stopping can mean blocking a gap).
'hatred' becomes 'animus' (animus is a kind of hatred).
'o' going inside 'animus' is 'animous'.
'un'+'animous'='UNANIMOUS'
'it's' acts as a link.
(Other definitions for unanimous that I've seen before include "Acting together" , "no-one disagreeing" , "Without one dissenter" , "in complete agreement" , "All in agreement, no exceptions" .)