Live in Bucharest (3)
I believe the answer is:
are
'live' is the definition.
(both can mean exist)
'in bucharest' is the wordplay.
'in' indicates a hidden word.
'ARE' is hidden within 'bucharest'.
(Other definitions for are that I've seen before include "Exist; square measure" , "(We/you/they) exist" , "Era (anag.)" , "Is, in the plural" , "(They/you/we) exist" .)