Performance outside called insane (8)
I believe the answer is:
deranged
'insane' is the definition.
('deranged' can be similar in meaning to 'insane')
'performance outside called' is the wordplay.
'performance' becomes 'deed' (I've seen this in other clues).
'outside' indicates putting letters inside.
'called' becomes 'rang' ('ring' can be a synonym of 'call').
'deed' enclosing 'rang' is 'DERANGED'.
(Other definitions for deranged that I've seen before include "Mentally unbalanced" , "Crazy" , "Lunatic" , "Upset" , "Crackpot" .)