Where one may be driven mad? (2,3,4)
I believe the answer is:
up the wall
'mad?' is the definition.
(I've seen this before)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for up the wall that I've seen before include "Where climbers go" , "wild" , "Where espaliers run" , "Where Spiderman may go" , "Distracted, mad" .)