Battle 4, perhaps, to stop in London (9,6)
'stop in london' is the definition.
(stop on London Underground)
'battle 4 perhaps' is the wordplay.
'battle' becomes 'trafalgar' (Trafalgar is an example).
'4 perhaps' becomes 'square'.
'trafalgar'+'square'='TRAFALGAR SQUARE'
'to' acts as a link.
(Other definitions for trafalgar square that I've seen before include "Public space in central London" , "somewhere in London" , "ground near Charing Cross" .)
'battle' is the definition.
(Trafalgar is an example)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for trafalgar that I've seen before include "Public space in central London" , "Nelson battle and London Square" , "Cape" , "Nelson's eighteen hundred and five victory" , "Battle won by Nelson in 1805" .)