Group of countries involved in review of protocol basically (4)
I believe the answer is:
bloc
'group of countries' is the definition.
(group of associated nations, eg the Eastern bloc)
'involved in review of protocol basically' is the wordplay.
'review of' shows that the letters should be reversed in order.
'involved in' indicates a hidden word.
'colb' can be found hidden inside 'protocol basically'.
'colb' back-to-front is 'BLOC'.
(Other definitions for bloc that I've seen before include "-- Forsyth, entertainer" , "Group of parties or countries united in common interest - sounds wooden" , "Combination of parties or countries" , "Alliance - coalition" , "Group of allied nations" .)