Had to be mad (9)
I believe the answer is:
possessed
I believe this is a double definition.
'had' is the first definition.
('possess' can be a synonym of 'have')
'mad' is the second definition.
(thesaurus)
'to be' acts as a link.
(Other definitions for possessed that I've seen before include "It's collected" , "held as property" , "Demented" , "Enjoyed" , "being under a spell" .)