Change the last word daughter expressed, heartlessly (9)
I believe the answer is:
amendment
'change' is the definition.
(amendment is a kind of change)
'the last word daughter expressed heartlessly' is the wordplay.
'the last word' becomes 'amen' (I've seen this before).
'daughter' becomes 'd'.
'expressed heartlessly' becomes 'ment' (I am not sure about this - if you are sure you should believe this answer much more).
'amen'+'d'+'ment'='AMENDMENT'
Can you help me to learn more?
(Other definitions for amendment that I've seen before include "Statement added to or revising a document" , "a bit of a change!" , "Correction" , "Addition or alteration, to a motion or official document, say" , "Change designed to improve a text" .)