Activity outside called mad (8)
I believe the answer is:
deranged
'mad' is the definition.
(I've seen this before)
'activity outside called' is the wordplay.
'activity' becomes 'deed' (I've seen this in other clues).
'outside' means one lot of letters goes inside another.
'called' becomes 'rang' ('ring' can be a synonym of 'call').
'deed' placed around 'rang' is 'DERANGED'.
(Other definitions for deranged that I've seen before include "Made insane" , "bananas" , "Disordered, mentally perhaps" , "Crackpot" , "totally without reason" .)