Energy-packing bars and maybe canned food (5)
I believe the answer is:
beans
'and maybe canned food' is the definition.
I can't tell whether this definition defines the answer.
'energy-packing bars' is the wordplay.
'energy' becomes 'e' (physics symbol as in E=mc2).
'packing' is an insertion indicator.
'bars' becomes 'bans' (ban can mean to bar or forbid).
'e' put into 'bans' is 'BEANS'.
Can you help me to learn more?
(Other definitions for beans that I've seen before include "Pulses, tomato sauce and grilled bread" , "Haricots for instance" , "Haricots, e.g." , "Nothing at all in US" , "Coffee seeds" .)