Battle and London Square (9)
I believe the answer is:
trafalgar
'battle and london square' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for trafalgar that I've seen before include "19th century battle" , "Nelson battle and London Square" , "Battle won by Nelson in 1805" , "London Square and Nelson sea-battle" , "Public space in central London" .)