London landmark (9,4)
I believe the answer is:
admiralty arch
'london landmark' is the definition.
(structure in central London)
This is all the clue.
(Other definitions for admiralty arch that I've seen before include "Feature over The Mall" , "It stands at the Trafalgar Sq. end of the Mall" , "Entrance to The Mall off Trafalgar Square" , "building in London" , "Building between The Mall and Trafalgar Square" .)