Called during act -- that's insane (8)
I believe the answer is:
deranged
'insane' is the definition.
('deranged' can be similar in meaning to 'insane')
'called during act' is the wordplay.
'called' becomes 'rang' ('ring' can be a synonym of 'call').
'during' is an insertion indicator.
'act' becomes 'deed' (deed is a kind of act).
'rang' placed into 'deed' is 'DERANGED'.
'that's' acts as a link.
(Other definitions for deranged that I've seen before include "bananas" , "Disordered; insane" , "Crazy" , "Disordered, mentally perhaps" , "Mentally unbalanced" .)