City in Czechoslovakia (4)
I believe the answer is:
oslo
'city' is the definition.
(capital of Norway)
'in czechoslovakia' is the wordplay.
'in' indicates a hidden word.
'OSLO' can be found hidden inside 'czechoslovakia'.
(Other definitions for oslo that I've seen before include "Solo in Norway?" , "Go solo to European capital" , "Former Christiania" , "Location" , "City in Norway" .)