European city industrial action with no opening or closing (4)
I believe the answer is:
oslo
'european city' is the definition.
(capital of Norway)
'industrial action with no opening or closing' is the wordplay.
'industrial action' becomes 'goslow' (type of union action in the UK).
'with no opening or closing' indicates the central letters.
The centre of 'goslow' is 'OSLO'.
(Other definitions for oslo that I've seen before include "Capital of Norway" , "Scandinavian capital" , "Northern city" , "Nordic city" , "European capital, known until 1924 as Christiania" .)