Row about British flower (5)
I believe the answer is:
tiber
'flower' is the definition.
(River Tiber in Italy)
'row about british' is the wordplay.
'row' becomes 'tier' (a tier is a row of things).
'about' is an insertion indicator.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'tier' going around 'b' is 'TIBER'.
(Other definitions for tiber that I've seen before include "divides Rome" , "Roman river" , "The flower of Rome" , "Rome's river" , "Italian banker" .)