Agent wants old books put in different container (5)
I believe the answer is:
repot
'put in different container' is the definition.
(put in another pot)
'agent wants old books' is the wordplay.
'agent' becomes 'rep' (short for representative).
'wants' means one lot of letters go next to another.
'old books' becomes 'OT' (Old Testament).
'rep'+'ot'='REPOT'
(Other definitions for repot that I've seen before include "Move plant" , "Transplant" , "place somewhere new to put down roots" , "plant in another location" , "to fit into new container" .)