Empty container in a prison redesigned for waste material (5,4)
I believe the answer is:
scrap iron
'for waste material' is the definition.
'empty container in a prison redesigned' is the wordplay.
'empty' says to hollow out the word (remove centre letters).
'in' means one lot of letters goes inside another.
'redesigned' indicates anagramming the letters.
'container' with its middle removed is 'cr'.
'a'+'prison'='aprison'
'aprison' is an anagram of 'sapiron'.
'cr' placed within 'sapiron' is 'SCRAP-IRON'.
(Other definitions for scrap iron that I've seen before include "Discarded metal" , "Waste metal for melting down" , "for recycling" , "rubbish" .)