A container that may be rifled (6)
I believe the answer is:
barrel
'a container' is the definition.
(barrel is a kind of container)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for barrel that I've seen before include "VAT?" , "Oil or beer container" , "Round wooden vessel." , "Beer cask" , "Wood vessel; part of horse" .)