Country organising a trial, USA (9)
I believe the answer is:
australia
'country' is the definition.
(I know that Australia is a country)
'organising a trial usa' is the wordplay.
'organising' indicates an anagram.
'a'+'trial'+'usa'='atrialusa'
'atrialusa' with letters rearranged gives 'AUSTRALIA'.
(Other definitions for australia that I've seen before include "A US lariat can be found in this country, strangely" , "Largest island in the world" , "big country" , "A land down under" , "Island continent" .)