Container of riches, treasure, perhaps (5)
I believe the answer is:
chest
'container' is the definition.
(I know that chest is a type of box)
'of riches treasure perhaps' is the wordplay.
'of' says the answer is hidden in the clue.
'CHEST' can be found hidden inside 'riches treasure perhaps'.
(Other definitions for chest that I've seen before include "Strongbox; sternum" , "Bust" , "ark" , "Trunk or crate" , "Treasure box?" .)