Alliance in Zagreb locale (4)
I believe the answer is:
bloc
'alliance' is the definition.
(I know that bloc is a type of alliance)
'in zagreb locale' is the wordplay.
'in' indicates the answer is hidden within the clue.
'BLOC' can be found hidden inside 'zagreb locale'.
(Other definitions for bloc that I've seen before include "Political coalition" , "Political grouping of countries" , "Allied country group" , "People cooperating" , "Political group of nations" .)