Replacement comes from butchers but it's suet! (10)
I believe the answer is:
substitute
'replacement' is the definition.
('substitute' can be a synonym of 'replacement')
'butchers but it's suet' is the wordplay.
'butchers' is an anagram indicator (I've seen 'butcher' mean this).
'but'+'its'+'suet'='butitssuet'
'butitssuet' anagrammed gives 'SUBSTITUTE'.
'comes from' is the link.
(Other definitions for substitute that I've seen before include "deputy" , "Replacement" , "Put in place of another" , "Reserve" , "Stand-in" .)