In Laos look for the capital city (4)
I believe the answer is:
oslo
'the capital city' is the definition.
(capital of Norway)
'in laos look for' is the wordplay.
'in' indicates a hidden word.
'OSLO' is hidden within 'laos look for'.
(Other definitions for oslo that I've seen before include "Scandinavian city" , "Norway's capital city" , "Scandinavian capital" , "City in Norway" , "Norwegian chief port" .)