Chest, coffer (3)
I believe the answer is:
ark
This clue is a double definition.
'chest' is the first definition.
(historical term for a chest)
'coffer' is the second definition.
(I've seen this before)
(Other definitions for ark that I've seen before include "Large vessel" , "Boat built to withstand floods" , "Noah's boat" , "old vessel" , "Rescue ship" .)