Encountered police in London (3)
I believe the answer is:
met
This clue might be a double definition.
'encountered' is the first definition.
('meet' can be a synonym of 'encounter')
'police in london' is the second definition.
'met' can be an answer for 'police' (London Metropolitan Police). I'm unsure of the 'in london' bit.
Can you help me to learn more?
(Other definitions for met that I've seen before include "Came across - police in London" , "Encountered by chance or arrangement" , "Encountered pro tem" , "satisfied" , "gathered together" .)