At sixes and sevens, as nine crazy! (6)
I believe the answer is:
insane
'crazy' is the definition.
('insane' can be similar in meaning to 'crazy')
'at sixes and sevens as nine' is the wordplay.
'at sixes and sevens' indicates an anagram.
'as'+'nine'='asnine'
'asnine' with letters rearranged gives 'INSANE'.
(Other definitions for insane that I've seen before include "Out of one's mind" , "Wild < cuckoo < cracked" , "Deranged, crazy" , "Quite mad" , "nuts" .)