Mean to change the last word (4)
'the last word' is the definition.
(I've seen this before)
'mean to change' is the wordplay.
'to change' indicates an anagram.
'mean' is an anagram of 'AMEN'.
(Other definitions for amen that I've seen before include "Name for end to prayer", "Final word in prayer", "Approve", "Word of approval", "Last word of prayer".)