Hamper from ex-students with one who skipped school about to replace case from Amazon (8)
I believe the answer is:
obstruct
'hamper' is the definition.
(I've seen this before)
I don't understand the remainder of the clue.
(Other definitions for obstruct that I've seen before include "Impede - block" , "Get in the way of" , "Block the passage or shut out the view" , "Hinder or impede" , "Stymie" .)