Formerly was victorious, we hear — it’s brought up by the writer (3-4)
I believe the answer is:
one-time
'formerly' is the definition.
'was victorious we hear it's brought up by the writer' is the wordplay.
'was victorious' becomes 'won' (I've seen this before).
'we hear' shows a homophone (sound like).
'brought up' says the letters should be written backwards (down clues only).
'by' means one lot of letters go next to another.
'the writer' becomes 'me' (the person who is writing these clues).
'won' sounds like 'one'.
'it' back-to-front is 'ti'.
'one'+'ti'+'me'='ONE-TIME'
(Other definitions for one-time that I've seen before include "Relating to a single occasion" , "Former" .)