Range of political blocs announced (8)
I believe the answer is:
caucasus
'range' is the definition.
(Caucasus Mountains is a mountain range)
'political blocs announced' is the wordplay.
'political blocs' becomes 'caucuses' (a caucus is a political grouping).
'announced' indicates a 'sounds like' (homophone) clue.
'caucuses' sounds like 'CAUCASUS'.
'of' is the link.
(Other definitions for caucasus that I've seen before include "Mountainous area between Caspian and Black seas" , "Mountain system between Black and Caspian seas" , "Region of SE Europe" , "Mountain region between Caspian and Black seas" , "Region including Georgia, Armenia, etc" .)