United achieved victory, we hear (3)
I believe the answer is:
one
'united' is the definition.
(as in a phrase like 'we are one')
'achieved victory we hear' is the wordplay.
'achieved victory' becomes 'won'.
'we hear' indicates a 'sounds like' (homophone) clue.
'won' is a homophone of 'ONE'.
(Other definitions for one that I've seen before include "Sole; number" , "Hour after midnight" , "joke" , "Identical; number" , "If upper-class, perhaps I" .)