Final word not entirely correct (4)
I believe the answer is:
amen
'final word' is the definition.
(last word in a prayer)
'not entirely correct' is the wordplay.
'not entirely' means to remove the last letter.
'correct' becomes 'amend' (amending is a kind of correcting).
'amend' with its final letter taken away is 'AMEN'.
(Other definitions for amen that I've seen before include "prayer's ending" , "Last word of prayer" , "Conclusion of prayer" , "Churchgoer's assent?" , "Word at the end of a prayer" .)