What broken door might be -- off the wall! (8)
I believe the answer is:
unhinged
I believe this is a double definition.
'what broken door might be' is the first definition.
(as in a door that's off its hinges)
'off the wall' is the second definition.
(both can mean crazy)
(Other definitions for unhinged that I've seen before include "not flapping?" , "Deranged" , "End I hung out to be mentally unbalanced" , "Mentally unbalanced like defective door?" , "characteristic of door after dislodgement?" .)