Former wrong item followed on final message (3-4)
I believe the answer is:
one-time
'former' is the definition.
(I know that former can be written as one-time)
'wrong item followed on final message' is the wordplay.
'wrong' is an anagram indicator.
'followed' says to put letters next to each other.
'final' suggests the final letters.
The final letter of 'message' is 'e'.
'item' with letters rearranged gives 'etim'.
'etim' put after 'on' is 'onetim'.
'onetim'+'e'='ONE-TIME'
(Other definitions for one-time that I've seen before include "Relating to a single occasion" , "Former" .)