A victory on a flower (4)
I believe the answer is:
avon
'a flower' is the definition.
(River Avon - something which flows)
'a victory on' is the wordplay.
'victory' becomes 'v'.
'a'+'v'+'on'='AVON'
(Other definitions for avon that I've seen before include "Stratford's river" , "English river flowing through Stratford" , "Shakespeare was known as the Bard of . . . ." , "River joining Bath with Bristol" , "River of the Bard" .)