Not a crazy organisation (4)
I believe the answer is:
nato
'organisation' is the definition.
(NATO is an example)
'not a crazy' is the wordplay.
'crazy' indicates an anagram.
'not'+'a'='nota'
'nota' is an anagram of 'NATO'.
(Other definitions for nato that I've seen before include "Transatlantic alliance" , "US/Europe alliance" , "Military alliance (acronym)" , "Military organization" , "Atlantic alliance (abbr.)" .)