Alliance at start letting each acceding Government use everything (6)
I believe the answer is:
league
'alliance' is the definition.
(thesaurus)
'start letting each acceding government use everything' is the wordplay.
'start' suggests taking the first letters.
The initial letters of 'letting each acceding government use everything' is 'LEAGUE'.
'at' is the link.
(Other definitions for league that I've seen before include "Federation" , "Group of clubs; distance" , "Group of sports clubs in an organised championship" , "Group in football" , "Association - old measure of distance" .)