Humpty Dumpty's perch (4)
I believe the answer is:
wall
'humpty dumpty's perch' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for wall that I've seen before include "Brick fence" , "Room divider" , "that may consist of many courses" , "Barrier, internal or external" , "Side of building" .)