Capital of Laos: Louangphabang? (4)
I believe the answer is:
oslo
'capital' is the definition.
(capital of Norway)
'of laos louangphabang?' is the wordplay.
'of' indicates a hidden word.
'OSLO' is hidden within 'laos louangphabang'.
(Other definitions for oslo that I've seen before include "Northern city" , "Location" , "foreign port" , "City in Norway" , "European capital, known until 1924 as Christiania" .)