Change the last word on front of dossier (5)
I believe the answer is:
amend
'change' is the definition.
(amending is a kind of changing)
'last word on front of dossier' is the wordplay.
'last word' becomes 'amen' (last word in a prayer).
'on front of' says to take the initial letters.
The initial letter of 'dossier' is 'd'.
'amen'+'d'='AMEND'
'the' acts as a link.
(Other definitions for amend that I've seen before include "Change, alter" , "Make small changes to" , "Change for the better" , "Alter in writing" , "Make small improvements to" .)