Working party in Lisbon evacuated capital (6)
I believe the answer is:
london
'capital' is the definition.
(capital of the United Kingdom)
'working party in lisbon evacuated' is the wordplay.
'working' becomes 'on' (on can mean working or activated).
'party' becomes 'do' (do is a kind of party).
'in' indicates putting letters inside.
'evacuated' suggests removing the centre.
'lisbon' with its middle taken out is 'ln'.
'on'+'do'='ondo'
'ondo' put within 'ln' is 'LONDON'.
(Other definitions for london that I've seen before include "US writer" , "UK's capital" , "British capital" , "- Clay; - pride; - plane" , "City for the non-old, oddly" .)