Top removed from dismantled casings and put in the post (6)
I believe the answer is:
assign
'the post' is the definition.
(I've seen this in another clue)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for assign that I've seen before include "Set aside for a specific purpose" , "Select and appoint for task" , "share out" , "Allot, allocate" , "Make over" .)