One bumped off in fighting somewhere in London (5)
I believe the answer is:
acton
'somewhere in london' is the definition.
(I've seen this before)
'one bumped off in fighting' is the wordplay.
'one' becomes 'i' (Roman numeral).
'bumped off in' is a deletion indicator.
'fighting' becomes 'action' (as in military action).
'action' with 'i' taken away is 'ACTON'.
(Other definitions for acton that I've seen before include "Gladstone's adviser" , "District of West London" , "Respond in accordance with - London district" , "London area" , "Part of the London borough of Ealing - British historian, d. 1902" .)