Close to scene, police in charge encouraging evacuation (6)
I believe the answer is:
emetic
'encouraging evacuation' is the definition.
(emetic means causing vomiting)
'close to scene police in charge' is the wordplay.
'close to' says to take the final letters (the close/ending of).
'police' becomes 'met' (London Metropolitan Police).
'in charge' becomes 'ic' (abbreviation for 'in charge').
The last letter of 'scene' is 'e'.
'e'+'met'+'ic'='EMETIC'
(Other definitions for emetic that I've seen before include "It makes one sick" , "Causing to vomit" , "inducing sickness" , "Medicine to make someone throw up" , "Something that causes vomiting" .)